diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 04179b5..1cffd4d 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -24,7 +24,11 @@ jobs:
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
+
+      - name: Lint
+        uses: cclauss/GitHub-Action-for-pylint@master
+        with:
+          args: "pylint src/vcs/"
 
       - name: Install dependencies
         run: sudo apt-get -y install appstream appstream-util desktop-file-utils gettext
diff --git a/.pylintrc b/.pylintrc
new file mode 100644
index 0000000..296041c
--- /dev/null
+++ b/.pylintrc
@@ -0,0 +1,584 @@
+[MASTER]
+
+# A comma-separated list of package or module names from where C extensions may
+# be loaded. Extensions are loading into the active Python interpreter and may
+# run arbitrary code.
+extension-pkg-allow-list=
+
+# A comma-separated list of package or module names from where C extensions may
+# be loaded. Extensions are loading into the active Python interpreter and may
+# run arbitrary code. (This is an alternative name to extension-pkg-allow-list
+# for backward compatibility.)
+extension-pkg-whitelist=
+
+# Return non-zero exit code if any of these messages/categories are detected,
+# even if score is above --fail-under value. Syntax same as enable. Messages
+# specified are enabled, while categories only check already-enabled messages.
+fail-on=
+
+# Specify a score threshold to be exceeded before program exits with error.
+fail-under=10.0
+
+# Files or directories to be skipped. They should be base names, not paths.
+ignore=CVS
+
+# Add files or directories matching the regex patterns to the ignore-list. The
+# regex matches against paths.
+ignore-paths=
+
+# Files or directories matching the regex patterns are skipped. The regex
+# matches against base names, not paths.
+ignore-patterns=
+
+# Python code to execute, usually for sys.path manipulation such as
+# pygtk.require().
+#init-hook=
+
+# Use multiple processes to speed up Pylint. Specifying 0 will auto-detect the
+# number of processors available to use.
+jobs=1
+
+# Control the amount of potential inferred values when inferring a single
+# object. This can help the performance when dealing with large functions or
+# complex, nested conditions.
+limit-inference-results=100
+
+# List of plugins (as comma separated values of python module names) to load,
+# usually to register additional checkers.
+load-plugins=
+
+# Pickle collected data for later comparisons.
+persistent=yes
+
+# Min Python version to use for version dependend checks. Will default to the
+# version used to run pylint.
+py-version=3.9
+
+# When enabled, pylint would attempt to guess common misconfiguration and emit
+# user-friendly hints instead of false-positive error messages.
+suggestion-mode=yes
+
+# Allow loading of arbitrary C extensions. Extensions are imported into the
+# active Python interpreter and may run arbitrary code.
+unsafe-load-any-extension=no
+
+
+[MESSAGES CONTROL]
+
+# Only show warnings with the listed confidence levels. Leave empty to show
+# all. Valid levels: HIGH, INFERENCE, INFERENCE_FAILURE, UNDEFINED.
+confidence=
+
+# Disable the message, report, category or checker with the given id(s). You
+# can either give multiple identifiers separated by comma (,) or put this
+# option multiple times (only on the command line, not in the configuration
+# file where it should appear only once). You can also use "--disable=all" to
+# disable everything first and then reenable specific checks. For example, if
+# you want to run only the similarities checker, you can use "--disable=all
+# --enable=similarities". If you want to run only the classes checker, but have
+# no Warning level messages displayed, use "--disable=all --enable=classes
+# --disable=W".
+disable=raw-checker-failed,
+        bad-inline-option,
+        locally-disabled,
+        file-ignored,
+        suppressed-message,
+        useless-suppression,
+        deprecated-pragma,
+        use-symbolic-message-instead,
+
+        # temporary silenced messages
+        invalid-name,
+        missing-module-docstring,
+        missing-class-docstring,
+        missing-function-docstring,
+        import-error,
+        no-self-use,
+        too-many-branches,
+        too-many-locals,
+        too-many-statements,
+        too-many-nested-blocks,
+        too-few-public-methods,
+        unused-argument,
+        fixme,
+        unnecessary-dict-index-lookup,
+        duplicate-code
+
+# Enable the message, report, category or checker with the given id(s). You can
+# either give multiple identifier separated by comma (,) or put this option
+# multiple time (only on the command line, not in the configuration file where
+# it should appear only once). See also the "--disable" option for examples.
+enable=c-extension-no-member
+
+
+[REPORTS]
+
+# Python expression which should return a score less than or equal to 10. You
+# have access to the variables 'error', 'warning', 'refactor', and 'convention'
+# which contain the number of messages in each category, as well as 'statement'
+# which is the total number of statements analyzed. This score is used by the
+# global evaluation report (RP0004).
+evaluation=10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10)
+
+# Template used to display messages. This is a python new-style format string
+# used to format the message information. See doc for all details.
+#msg-template=
+
+# Set the output format. Available formats are text, parseable, colorized, json
+# and msvs (visual studio). You can also give a reporter class, e.g.
+# mypackage.mymodule.MyReporterClass.
+output-format=text
+
+# Tells whether to display a full report or only the messages.
+reports=no
+
+# Activate the evaluation score.
+score=yes
+
+
+[REFACTORING]
+
+# Maximum number of nested blocks for function / method body
+max-nested-blocks=5
+
+# Complete name of functions that never returns. When checking for
+# inconsistent-return-statements if a never returning function is called then
+# it will be considered as an explicit return statement and no message will be
+# printed.
+never-returning-functions=sys.exit,argparse.parse_error
+
+
+[BASIC]
+
+# Naming style matching correct argument names.
+argument-naming-style=snake_case
+
+# Regular expression matching correct argument names. Overrides argument-
+# naming-style.
+#argument-rgx=
+
+# Naming style matching correct attribute names.
+attr-naming-style=snake_case
+
+# Regular expression matching correct attribute names. Overrides attr-naming-
+# style.
+#attr-rgx=
+
+# Bad variable names which should always be refused, separated by a comma.
+bad-names=foo,
+          bar,
+          baz,
+          toto,
+          tutu,
+          tata
+
+# Bad variable names regexes, separated by a comma. If names match any regex,
+# they will always be refused
+bad-names-rgxs=
+
+# Naming style matching correct class attribute names.
+class-attribute-naming-style=any
+
+# Regular expression matching correct class attribute names. Overrides class-
+# attribute-naming-style.
+#class-attribute-rgx=
+
+# Naming style matching correct class constant names.
+class-const-naming-style=UPPER_CASE
+
+# Regular expression matching correct class constant names. Overrides class-
+# const-naming-style.
+#class-const-rgx=
+
+# Naming style matching correct class names.
+class-naming-style=PascalCase
+
+# Regular expression matching correct class names. Overrides class-naming-
+# style.
+#class-rgx=
+
+# Naming style matching correct constant names.
+const-naming-style=UPPER_CASE
+
+# Regular expression matching correct constant names. Overrides const-naming-
+# style.
+#const-rgx=
+
+# Minimum line length for functions/classes that require docstrings, shorter
+# ones are exempt.
+docstring-min-length=-1
+
+# Naming style matching correct function names.
+function-naming-style=snake_case
+
+# Regular expression matching correct function names. Overrides function-
+# naming-style.
+#function-rgx=
+
+# Good variable names which should always be accepted, separated by a comma.
+good-names=i,
+           j,
+           k,
+           ex,
+           Run,
+           _
+
+# Good variable names regexes, separated by a comma. If names match any regex,
+# they will always be accepted
+good-names-rgxs=
+
+# Include a hint for the correct naming format with invalid-name.
+include-naming-hint=no
+
+# Naming style matching correct inline iteration names.
+inlinevar-naming-style=any
+
+# Regular expression matching correct inline iteration names. Overrides
+# inlinevar-naming-style.
+#inlinevar-rgx=
+
+# Naming style matching correct method names.
+method-naming-style=snake_case
+
+# Regular expression matching correct method names. Overrides method-naming-
+# style.
+#method-rgx=
+
+# Naming style matching correct module names.
+module-naming-style=snake_case
+
+# Regular expression matching correct module names. Overrides module-naming-
+# style.
+#module-rgx=
+
+# Colon-delimited sets of names that determine each other's naming style when
+# the name regexes allow several styles.
+name-group=
+
+# Regular expression which should only match function or class names that do
+# not require a docstring.
+no-docstring-rgx=^_
+
+# List of decorators that produce properties, such as abc.abstractproperty. Add
+# to this list to register other decorators that produce valid properties.
+# These decorators are taken in consideration only for invalid-name.
+property-classes=abc.abstractproperty
+
+# Naming style matching correct variable names.
+variable-naming-style=snake_case
+
+# Regular expression matching correct variable names. Overrides variable-
+# naming-style.
+#variable-rgx=
+
+
+[FORMAT]
+
+# Expected format of line ending, e.g. empty (any line ending), LF or CRLF.
+expected-line-ending-format=
+
+# Regexp for a line that is allowed to be longer than the limit.
+ignore-long-lines=^\s*(# )?<?https?://\S+>?$
+
+# Number of spaces of indent required inside a hanging or continued line.
+indent-after-paren=4
+
+# String used as indentation unit. This is usually "    " (4 spaces) or "\t" (1
+# tab).
+indent-string='    '
+
+# Maximum number of characters on a single line.
+max-line-length=100
+
+# Maximum number of lines in a module.
+max-module-lines=1000
+
+# Allow the body of a class to be on the same line as the declaration if body
+# contains single statement.
+single-line-class-stmt=no
+
+# Allow the body of an if to be on the same line as the test if there is no
+# else.
+single-line-if-stmt=no
+
+
+[LOGGING]
+
+# The type of string formatting that logging methods do. `old` means using %
+# formatting, `new` is for `{}` formatting.
+logging-format-style=old
+
+# Logging modules to check that the string format arguments are in logging
+# function parameter format.
+logging-modules=logging
+
+
+[MISCELLANEOUS]
+
+# List of note tags to take in consideration, separated by a comma.
+notes=FIXME,
+      XXX,
+      TODO
+
+# Regular expression of note tags to take in consideration.
+#notes-rgx=
+
+
+[SIMILARITIES]
+
+# Comments are removed from the similarity computation
+ignore-comments=yes
+
+# Docstrings are removed from the similarity computation
+ignore-docstrings=yes
+
+# Imports are removed from the similarity computation
+ignore-imports=no
+
+# Signatures are removed from the similarity computation
+ignore-signatures=no
+
+# Minimum lines number of a similarity.
+min-similarity-lines=4
+
+
+[SPELLING]
+
+# Limits count of emitted suggestions for spelling mistakes.
+max-spelling-suggestions=4
+
+# Spelling dictionary name. Available dictionaries: en_AG (hunspell), en_AU
+# (hunspell), en_BS (hunspell), en_BW (hunspell), en_BZ (hunspell), en_CA
+# (hunspell), en_DK (hunspell), en_GB (hunspell), en_GH (hunspell), en_HK
+# (hunspell), en_IE (hunspell), en_IN (hunspell), en_JM (hunspell), en_MW
+# (hunspell), en_NA (hunspell), en_NG (hunspell), en_NZ (hunspell), en_PH
+# (hunspell), en_SG (hunspell), en_TT (hunspell), en_US (hunspell), en_ZA
+# (hunspell), en_ZM (hunspell), en_ZW (hunspell), fr_BE (hunspell), fr_CA
+# (hunspell), fr_CH (hunspell), fr_FR (hunspell), fr_LU (hunspell), fr_MC
+# (hunspell).
+spelling-dict=
+
+# List of comma separated words that should be considered directives if they
+# appear and the beginning of a comment and should not be checked.
+spelling-ignore-comment-directives=fmt: on,fmt: off,noqa:,noqa,nosec,isort:skip,mypy:
+
+# List of comma separated words that should not be checked.
+spelling-ignore-words=
+
+# A path to a file that contains the private dictionary; one word per line.
+spelling-private-dict-file=
+
+# Tells whether to store unknown words to the private dictionary (see the
+# --spelling-private-dict-file option) instead of raising a message.
+spelling-store-unknown-words=no
+
+
+[STRING]
+
+# This flag controls whether inconsistent-quotes generates a warning when the
+# character used as a quote delimiter is used inconsistently within a module.
+check-quote-consistency=no
+
+# This flag controls whether the implicit-str-concat should generate a warning
+# on implicit string concatenation in sequences defined over several lines.
+check-str-concat-over-line-jumps=no
+
+
+[TYPECHECK]
+
+# List of decorators that produce context managers, such as
+# contextlib.contextmanager. Add to this list to register other decorators that
+# produce valid context managers.
+contextmanager-decorators=contextlib.contextmanager
+
+# List of members which are set dynamically and missed by pylint inference
+# system, and so shouldn't trigger E1101 when accessed. Python regular
+# expressions are accepted.
+generated-members=
+
+# Tells whether missing members accessed in mixin class should be ignored. A
+# mixin class is detected if its name ends with "mixin" (case insensitive).
+ignore-mixin-members=yes
+
+# Tells whether to warn about missing members when the owner of the attribute
+# is inferred to be None.
+ignore-none=yes
+
+# This flag controls whether pylint should warn about no-member and similar
+# checks whenever an opaque object is returned when inferring. The inference
+# can return multiple potential results while evaluating a Python object, but
+# some branches might not be evaluated, which results in partial inference. In
+# that case, it might be useful to still emit no-member and other checks for
+# the rest of the inferred objects.
+ignore-on-opaque-inference=yes
+
+# List of class names for which member attributes should not be checked (useful
+# for classes with dynamically set attributes). This supports the use of
+# qualified names.
+ignored-classes=optparse.Values,thread._local,_thread._local
+
+# List of module names for which member attributes should not be checked
+# (useful for modules/projects where namespaces are manipulated during runtime
+# and thus existing member attributes cannot be deduced by static analysis). It
+# supports qualified module names, as well as Unix pattern matching.
+ignored-modules=
+
+# Show a hint with possible names when a member name was not found. The aspect
+# of finding the hint is based on edit distance.
+missing-member-hint=yes
+
+# The minimum edit distance a name should have in order to be considered a
+# similar match for a missing member name.
+missing-member-hint-distance=1
+
+# The total number of similar names that should be taken in consideration when
+# showing a hint for a missing member.
+missing-member-max-choices=1
+
+# List of decorators that change the signature of a decorated function.
+signature-mutators=
+
+
+[VARIABLES]
+
+# List of additional names supposed to be defined in builtins. Remember that
+# you should avoid defining new builtins when possible.
+additional-builtins=_
+
+# Tells whether unused global variables should be treated as a violation.
+allow-global-unused-variables=yes
+
+# List of names allowed to shadow builtins
+allowed-redefined-builtins=
+
+# List of strings which can identify a callback function by name. A callback
+# name must start or end with one of those strings.
+callbacks=cb_,
+          _cb
+
+# A regular expression matching the name of dummy variables (i.e. expected to
+# not be used).
+dummy-variables-rgx=_+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy|^ignored_|^unused_
+
+# Argument names that match this expression will be ignored. Default to name
+# with leading underscore.
+ignored-argument-names=_.*|^ignored_|^unused_
+
+# Tells whether we should check for unused import in __init__ files.
+init-import=no
+
+# List of qualified module names which can have objects that can redefine
+# builtins.
+redefining-builtins-modules=six.moves,past.builtins,future.builtins,builtins,io
+
+
+[CLASSES]
+
+# Warn about protected attribute access inside special methods
+check-protected-access-in-special-methods=no
+
+# List of method names used to declare (i.e. assign) instance attributes.
+defining-attr-methods=__init__,
+                      __new__,
+                      setUp,
+                      __post_init__
+
+# List of member names, which should be excluded from the protected access
+# warning.
+exclude-protected=_asdict,
+                  _fields,
+                  _replace,
+                  _source,
+                  _make
+
+# List of valid names for the first argument in a class method.
+valid-classmethod-first-arg=cls
+
+# List of valid names for the first argument in a metaclass class method.
+valid-metaclass-classmethod-first-arg=cls
+
+
+[DESIGN]
+
+# List of qualified class names to ignore when counting class parents (see
+# R0901)
+ignored-parents=
+
+# Maximum number of arguments for function / method.
+max-args=5
+
+# Maximum number of attributes for a class (see R0902).
+max-attributes=7
+
+# Maximum number of boolean expressions in an if statement (see R0916).
+max-bool-expr=5
+
+# Maximum number of branch for function / method body.
+max-branches=12
+
+# Maximum number of locals for function / method body.
+max-locals=15
+
+# Maximum number of parents for a class (see R0901).
+max-parents=7
+
+# Maximum number of public methods for a class (see R0904).
+max-public-methods=20
+
+# Maximum number of return / yield for function / method body.
+max-returns=6
+
+# Maximum number of statements in function / method body.
+max-statements=50
+
+# Minimum number of public methods for a class (see R0903).
+min-public-methods=2
+
+
+[IMPORTS]
+
+# List of modules that can be imported at any level, not just the top level
+# one.
+allow-any-import-level=
+
+# Allow wildcard imports from modules that define __all__.
+allow-wildcard-with-all=no
+
+# Analyse import fallback blocks. This can be used to support both Python 2 and
+# 3 compatible code, which means that the block might have code that exists
+# only in one or another interpreter, leading to false positives when analysed.
+analyse-fallback-blocks=no
+
+# Deprecated modules which should not be used, separated by a comma.
+deprecated-modules=
+
+# Output a graph (.gv or any supported image format) of external dependencies
+# to the given file (report RP0402 must not be disabled).
+ext-import-graph=
+
+# Output a graph (.gv or any supported image format) of all (i.e. internal and
+# external) dependencies to the given file (report RP0402 must not be
+# disabled).
+import-graph=
+
+# Output a graph (.gv or any supported image format) of internal dependencies
+# to the given file (report RP0402 must not be disabled).
+int-import-graph=
+
+# Force import order to recognize a module as part of the standard
+# compatibility libraries.
+known-standard-library=
+
+# Force import order to recognize a module as part of a third party library.
+known-third-party=enchant
+
+# Couples of modules and preferred modules, separated by a comma.
+preferred-modules=
+
+
+[EXCEPTIONS]
+
+# Exceptions that will emit a warning when being caught. Defaults to
+# "BaseException, Exception".
+overgeneral-exceptions=BaseException,
+                       Exception
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4e5b7b7..6b157f2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- Added a linter (pylint) and fixed some errors
+- Added a lint step in the CI
 
 ### Changed
 
diff --git a/src/diffuse.in b/src/diffuse.in
index dab1359..973f974 100755
--- a/src/diffuse.in
+++ b/src/diffuse.in
@@ -21,13 +21,12 @@
 
 import sys
 import gettext
-import locale
 
-pkgdatadir = '@pkgdatadir@'
-localedir = '@localedir@'
+PKGDATADIR = '@pkgdatadir@'
+LOCALEDIR = '@localedir@'
 
-sys.path.insert(1, pkgdatadir)
-gettext.install('diffuse', localedir)
+sys.path.insert(1, PKGDATADIR)
+gettext.install('diffuse', LOCALEDIR)
 
 if __name__ == '__main__':
     from diffuse import main
diff --git a/src/main.py b/src/main.py
index b291b19..278eb0b 100644
--- a/src/main.py
+++ b/src/main.py
@@ -55,10 +55,6 @@ from diffuse import utils
 from diffuse import constants
 from diffuse.vcs.vcs_registry import VcsRegistry
 
-if not hasattr(__builtins__, 'WindowsError'):
-    # define 'WindowsError' so 'except' statements will work on all platforms
-    WindowsError = IOError
-
 # avoid some dictionary lookups when string.whitespace is used in loops
 # this is sorted based upon frequency to speed up code for stripping whitespace
 whitespace = ' \t\n\r\x0b\x0c'
@@ -131,38 +127,6 @@ class SyntaxParser:
             start = end
         return state_name, blocks
 
-# split string into lines based upon DOS, Mac, and Unix line endings
-def splitlines(s):
-    # split on new line characters
-    temp, i, n = [], 0, len(s)
-    while i < n:
-        j = s.find('\n', i)
-        if j < 0:
-            temp.append(s[i:])
-            break
-        j += 1
-        temp.append(s[i:j])
-        i = j
-    # split on carriage return characters
-    ss = []
-    for s in temp:
-        i, n = 0, len(s)
-        while i < n:
-            j = s.find('\r', i)
-            if j < 0:
-                ss.append(s[i:])
-                break
-            j += 1
-            if j < n and s[j] == '\n':
-                j += 1
-            ss.append(s[i:j])
-            i = j
-    return ss
-
-# also recognise old Mac OS line endings
-def readlines(fd):
-    return strip_eols(splitlines(fd.read()))
-
 def readconfiglines(fd):
     return fd.read().replace('\r', '').split('\n')
 
@@ -1141,33 +1105,12 @@ def getFormat(ss):
                 flags |= UNIX_FORMAT
     return flags
 
-# returns the number of characters in the string excluding any line ending
-# characters
-def len_minus_line_ending(s):
-    if s is None:
-        return 0
-    n = len(s)
-    if s.endswith('\r\n'):
-        n -= 2
-    elif s.endswith('\r') or s.endswith('\n'):
-        n -= 1
-    return n
-
-# returns the string without the line ending characters
-def strip_eol(s):
-    if s is not None:
-        return s[:len_minus_line_ending(s)]
-
-# returns the list of strings without line ending characters
-def strip_eols(ss):
-    return [ strip_eol(s) for s in ss ]
-
 # convenience method to change the line ending of a string
 def convert_to_format(s, format):
     if s is not None and format != 0:
         old_format = getFormat([ s ])
         if old_format != 0 and (old_format & format) == 0:
-            s = strip_eol(s)
+            s = utils.strip_eol(s)
             # prefer the host line ending style
             if (format & DOS_FORMAT) and os.linesep == '\r\n':
                 s += os.linesep
@@ -1913,7 +1856,7 @@ class FileDiffViewer(Gtk.Grid):
     # This is an inline loop over self.characterWidth() for performance reasons.
     def stringWidth(self, s):
         if not self.prefs.getBool('display_show_whitespace'):
-            s = strip_eol(s)
+            s = utils.strip_eol(s)
         col = 0
         for c in s:
             try:
@@ -1965,7 +1908,7 @@ class FileDiffViewer(Gtk.Grid):
     def expand(self, s):
         visible = self.prefs.getBool('display_show_whitespace')
         if not visible:
-            s = strip_eol(s)
+            s = utils.strip_eol(s)
         tab_width = self.prefs.getInt('display_tab_width')
         col = 0
         result = []
@@ -2563,7 +2506,7 @@ class FileDiffViewer(Gtk.Grid):
             # hashes for non-null lines should start with '+' to distinguish
             # them from blank lines
             if pref('align_ignore_endofline'):
-                text = strip_eol(text)
+                text = utils.strip_eol(text)
             if pref('align_ignore_blanklines') and isBlank(text):
                 # consider all lines containing only white space as the same
                 return ''
@@ -2792,8 +2735,8 @@ class FileDiffViewer(Gtk.Grid):
         if text is None:
             text = ''
         # split the replacement text into lines
-        ss = splitlines(text)
-        if len(ss) == 0 or len(ss[-1]) != len_minus_line_ending(ss[-1]):
+        ss = utils.splitlines(text)
+        if len(ss) == 0 or len(ss[-1]) != utils.len_minus_line_ending(ss[-1]):
             ss.append('')
         # change the format to that of the target pane
         if pane.format == 0:
@@ -2807,7 +2750,7 @@ class FileDiffViewer(Gtk.Grid):
         lastcol = 0
         if len(ss) > 0:
             last = ss[-1]
-            if len(last) == len_minus_line_ending(last):
+            if len(last) == utils.len_minus_line_ending(last):
                 del ss[-1]
                 lastcol = len(last)
         cur_line = line0 + len(ss)
@@ -3200,7 +3143,7 @@ class FileDiffViewer(Gtk.Grid):
             x, y = -1, 0
         i = min(y // self.font_height, len(self.panes[f].lines))
         if self.mode == CHAR_MODE and f == self.current_pane:
-            text = strip_eol(self.getLineText(f, i))
+            text = utils.strip_eol(self.getLineText(f, i))
             j = self._getPickedCharacter(text, x, True)
             if extend:
                 si, sj = self.selection_line, self.selection_char
@@ -3241,7 +3184,7 @@ class FileDiffViewer(Gtk.Grid):
                     self.emit('mode_changed')
                 elif self.mode == CHAR_MODE and self.current_pane == f:
                     # select word
-                    text = strip_eol(self.getLineText(f, i))
+                    text = utils.strip_eol(self.getLineText(f, i))
                     if text is not None:
                         n = len(text)
                         j = self._getPickedCharacter(text, x, False)
@@ -3323,7 +3266,7 @@ class FileDiffViewer(Gtk.Grid):
             else:
                 s = s2
             if self.prefs.getBool('display_ignore_endofline'):
-                s = strip_eol(s)
+                s = utils.strip_eol(s)
 
             s1 = nullToEmpty(self.getCompareString(f, i))
             s2 = nullToEmpty(self.getCompareString(f + 1, i))
@@ -3394,7 +3337,7 @@ class FileDiffViewer(Gtk.Grid):
         s = line.getText()
         if s is not None:
             if self.prefs.getBool('display_ignore_endofline'):
-                s = strip_eol(s)
+                s = utils.strip_eol(s)
             if self.prefs.getBool('display_ignore_blanklines') and isBlank(s):
                 return None
             if self.prefs.getBool('display_ignore_whitespace'):
@@ -3906,7 +3849,7 @@ class FileDiffViewer(Gtk.Grid):
     # returns the maximum valid offset for a cursor position
     # cursors cannot be moved to the right of line ending characters
     def getMaxCharPosition(self, i):
-        return len_minus_line_ending(self.getLineText(self.current_pane, i))
+        return utils.len_minus_line_ending(self.getLineText(self.current_pane, i))
 
     # 'enter_align_mode' keybinding action
     def _line_mode_enter_align_mode(self):
@@ -4132,7 +4075,7 @@ class FileDiffViewer(Gtk.Grid):
                     # move the cursor to column 'col' if possible
                     s = self.getLineText(f, i)
                     if s is not None:
-                        s = strip_eol(s)
+                        s = utils.strip_eol(s)
                         idx = 0
                         for c in s:
                             w = self.characterWidth(idx, c)
@@ -4282,7 +4225,7 @@ class FileDiffViewer(Gtk.Grid):
                     self.recordEditMode()
                     for i in range(start, end + 1):
                         text = self.getLineText(f, i)
-                        if text is not None and len_minus_line_ending(text) > 0:
+                        if text is not None and utils.len_minus_line_ending(text) > 0:
                             # count spacing before the first non-whitespace character
                             j, w = 0, 0
                             while j < len(text) and text[j] in ' \t':
@@ -4807,7 +4750,7 @@ class FileDiffViewer(Gtk.Grid):
             text = self.getLineText(f, i)
             if text is not None:
                 # locate trailing whitespace
-                old_n = n = len_minus_line_ending(text)
+                old_n = n = utils.len_minus_line_ending(text)
                 while n > 0 and text[n - 1] in whitespace:
                     n -= 1
                 # update line if it changed
@@ -4914,7 +4857,7 @@ class FileDiffViewer(Gtk.Grid):
         self.recordEditMode()
         for i in range(start, end + 1):
             text = self.getLineText(f, i)
-            if text is not None and len_minus_line_ending(text) > 0:
+            if text is not None and utils.len_minus_line_ending(text) > 0:
                 # count spacing before the first non-whitespace character
                 j, w = 0, 0
                 while j < len(text) and text[j] in ' \t':
@@ -5628,8 +5571,8 @@ class Diffuse(Gtk.Window):
                         s, encoding = self.prefs.convertToUnicode(s)
                     else:
                         s = str(s, encoding=encoding)
-                    ss = splitlines(s)
-                except (IOError, OSError, UnicodeDecodeError, WindowsError, LookupError):
+                    ss = utils.splitlines(s)
+                except (IOError, OSError, UnicodeDecodeError, LookupError):
                     # FIXME: this can occur before the toplevel window is drawn
                     if rev is not None:
                         msg = _('Error reading revision %(rev)s of %(file)s.') % { 'rev': rev, 'file': name }
@@ -6460,7 +6403,7 @@ class Diffuse(Gtk.Window):
                             name, rev = spec
                             viewer.load(i, FileInfo(name, encoding, vcs, rev))
                         viewer.setOptions(options)
-                except (IOError, OSError, WindowsError):
+                except (IOError, OSError):
                     utils.logErrorAndDialog(_('Error retrieving commits for %s.') % (dn, ), self.get_toplevel())
 
     # create a new viewer for each modified file found in 'items'
@@ -6489,7 +6432,7 @@ class Diffuse(Gtk.Window):
                             name, rev = spec
                             viewer.load(i, FileInfo(name, encoding, vcs, rev))
                         viewer.setOptions(options)
-                except (IOError, OSError, WindowsError):
+                except (IOError, OSError):
                     utils.logErrorAndDialog(_('Error retrieving modifications for %s.') % (dn, ), self.get_toplevel())
 
     # close all tabs without differences
diff --git a/src/utils.py b/src/utils.py
index 9b8dadd..d499d6d 100644
--- a/src/utils.py
+++ b/src/utils.py
@@ -96,8 +96,8 @@ def relpath(a, b):
 # helper function prevent files from being confused with command line options
 # by prepending './' to the basename
 def safeRelativePath(abspath1, name, prefs, cygwin_pref):
-    s = os.path.join(os.curdir, utils.relpath(abspath1, os.path.abspath(name)))
-    if utils.isWindows():
+    s = os.path.join(os.curdir, relpath(abspath1, os.path.abspath(name)))
+    if isWindows():
         if prefs.getBool(cygwin_pref):
             s = s.replace('\\', '/')
         else:
@@ -182,6 +182,55 @@ def globEscape(s):
     m = dict([ (c, f'[{c}]') for c in '[]?*' ])
     return ''.join([ m.get(c, c) for c in s ])
 
+# returns the number of characters in the string excluding any line ending
+# characters
+def len_minus_line_ending(s):
+    if s is None:
+        return 0
+    n = len(s)
+    if s.endswith('\r\n'):
+        n -= 2
+    elif s.endswith('\r') or s.endswith('\n'):
+        n -= 1
+    return n
+
+# returns the string without the line ending characters
+def strip_eol(s):
+    if s is not None:
+        return s[:len_minus_line_ending(s)]
+
+# split string into lines based upon DOS, Mac, and Unix line endings
+def splitlines(s):
+    # split on new line characters
+    temp, i, n = [], 0, len(s)
+    while i < n:
+        j = s.find('\n', i)
+        if j < 0:
+            temp.append(s[i:])
+            break
+        j += 1
+        temp.append(s[i:j])
+        i = j
+    # split on carriage return characters
+    ss = []
+    for s in temp:
+        i, n = 0, len(s)
+        while i < n:
+            j = s.find('\r', i)
+            if j < 0:
+                ss.append(s[i:])
+                break
+            j += 1
+            if j < n and s[j] == '\n':
+                j += 1
+            ss.append(s[i:j])
+            i = j
+    return ss
+
+# also recognize old Mac OS line endings
+def readlines(fd):
+    return [ strip_eol(s) for s in splitlines(fd.read()) ]
+
 # use the program's location as a starting place to search for supporting files
 # such as icon and help documentation
 if hasattr(sys, 'frozen'):
diff --git a/src/vcs/cvs.py b/src/vcs/cvs.py
index 6b887bd..b39318f 100644
--- a/src/vcs/cvs.py
+++ b/src/vcs/cvs.py
@@ -41,11 +41,11 @@ class Cvs(VcsInterface):
                 if len(r):
                     prev = '.'.join(r)
             for k in sorted(names):
-                 if prev is None:
-                     k0 = None
-                 else:
-                     k0 = k
-                 result.append([ (k0, prev), (k, rev) ])
+                if prev is None:
+                    k0 = None
+                else:
+                    k0 = k
+                result.append([ (k0, prev), (k, rev) ])
         except ValueError:
             utils.logError(_('Error parsing revision %s.') % (rev, ))
         return result
@@ -73,7 +73,6 @@ class Cvs(VcsInterface):
                 if s[0] == 'R':
                     # removed
                     modified[k] = [ (k, prev), (None, None) ]
-                    pass
                 elif s[0] == 'A':
                     # added
                     modified[k] = [ (None, None), (k, None) ]
diff --git a/src/vcs/folder_set.py b/src/vcs/folder_set.py
index a674acc..9fe050e 100644
--- a/src/vcs/folder_set.py
+++ b/src/vcs/folder_set.py
@@ -42,4 +42,3 @@ class FolderSet:
             if abspath.startswith(f):
                 return True
         return False
-
diff --git a/src/vcs/git.py b/src/vcs/git.py
index 46e2903..5aabef5 100644
--- a/src/vcs/git.py
+++ b/src/vcs/git.py
@@ -65,7 +65,14 @@ class Git(VcsInterface):
 
     def getFolderTemplate(self, prefs, names):
         # build command
-        args = [ prefs.getString('git_bin'), 'status', '--porcelain', '-s', '--untracked-files=no', '--ignore-submodules=all' ]
+        args = [
+            prefs.getString('git_bin'),
+            'status',
+            '--porcelain',
+            '-s',
+            '--untracked-files=no',
+            '--ignore-submodules=all'
+        ]
         # build list of interesting files
         pwd = os.path.abspath(os.curdir)
         isabs = False
@@ -142,14 +149,13 @@ class Git(VcsInterface):
         return result
 
     def getRevision(self, prefs, name, rev):
+        relpath = utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/')
         return utils.popenRead(
             self.root,
             [
                 prefs.getString('git_bin'),
                 'show',
-                '{}:{}'.format(
-                    rev,
-                    utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/'))
+                f'{rev}:{relpath}'
             ],
             prefs,
             'git_bash')
diff --git a/src/vcs/hg.py b/src/vcs/hg.py
index cd42d92..5cf550e 100644
--- a/src/vcs/hg.py
+++ b/src/vcs/hg.py
@@ -32,7 +32,11 @@ class Hg(VcsInterface):
     def _getPreviousRevision(self, prefs, rev):
         if rev is None:
             if self.working_rev is None:
-                ss = utils.popenReadLines(self.root, [ prefs.getString('hg_bin'), 'id', '-i', '-t' ], prefs, 'hg_bash')
+                ss = utils.popenReadLines(
+                    self.root,
+                    [ prefs.getString('hg_bin'), 'id', '-i', '-t' ],
+                    prefs,
+                    'hg_bash')
                 if len(ss) != 1:
                     raise IOError('Unknown working revision')
                 ss = ss[0].split(' ')
@@ -81,7 +85,11 @@ class Hg(VcsInterface):
         return [ modified[k] for k in sorted(modified.keys()) ]
 
     def getCommitTemplate(self, prefs, rev, names):
-        return self._getCommitTemplate(prefs, names, [ 'log', '--template', 'A\t{file_adds}\nM\t{file_mods}\nR\t{file_dels}\n', '-r', rev ], rev)
+        return self._getCommitTemplate(
+            prefs,
+            names,
+            [ 'log', '--template', 'A\t{file_adds}\nM\t{file_mods}\nR\t{file_dels}\n', '-r', rev ],
+            rev)
 
     def getFolderTemplate(self, prefs, names):
         return self._getCommitTemplate(prefs, names, [ 'status', '-q' ], None)
diff --git a/src/vcs/mtn.py b/src/vcs/mtn.py
index f70f6f4..fc551f4 100644
--- a/src/vcs/mtn.py
+++ b/src/vcs/mtn.py
@@ -33,7 +33,11 @@ class Mtn(VcsInterface):
     def getCommitTemplate(self, prefs, rev, names):
         # build command
         vcs_bin = prefs.getString('mtn_bin')
-        ss = utils.popenReadLines(self.root, [ vcs_bin, 'automate', 'select', '-q', rev ], prefs, 'mtn_bash')
+        ss = utils.popenReadLines(
+            self.root,
+            [ vcs_bin, 'automate', 'select', '-q', rev ],
+            prefs,
+            'mtn_bash')
         if len(ss) != 1:
             raise IOError('Ambiguous revision specifier')
         args = [ vcs_bin, 'automate', 'get_revision', ss[0] ]
@@ -59,7 +63,7 @@ class Mtn(VcsInterface):
                     break
                 prev = arg1[1:-1]
                 continue
-            elif prev is None:
+            if prev is None:
                 continue
             if arg == 'delete':
                 # deleted file
@@ -88,7 +92,11 @@ class Mtn(VcsInterface):
         if removed or renamed:
             # remove directories
             removed_dirs = set()
-            for s in utils.popenReadLines(self.root, [ vcs_bin, 'automate', 'get_manifest_of', prev ], prefs, 'mtn_bash'):
+            for s in utils.popenReadLines(
+                self.root,
+                [ vcs_bin, 'automate', 'get_manifest_of', prev ],
+                prefs,
+                'mtn_bash'):
                 s = shlex.split(s)
                 if len(s) > 1 and s[0] == 'dir':
                     removed_dirs.add(s[1])
@@ -130,7 +138,14 @@ class Mtn(VcsInterface):
         fs = FolderSet(names)
         result = []
         pwd, isabs = os.path.abspath(os.curdir), False
-        args = [ prefs.getString('mtn_bin'), 'automate', 'inventory', '--no-ignored', '--no-unchanged', '--no-unknown' ]
+        args = [
+            prefs.getString('mtn_bin'),
+            'automate',
+            'inventory',
+            '--no-ignored',
+            '--no-unchanged',
+            '--no-unknown'
+        ]
         for name in names:
             isabs |= os.path.isabs(name)
         # build list of interesting files
@@ -168,7 +183,11 @@ class Mtn(VcsInterface):
                             k = utils.relpath(pwd, k)
                         added[k] = [ (None, None), (k, None) ]
                     processed = True
-                if 'rename_target' in s and 'file' in m.get('new_type', []) and len(m.get('old_path', [])) > 0:
+                if (
+                    'rename_target' in s and
+                    'file' in m.get('new_type', []) and
+                    len(m.get('old_path', [])) > 0
+                ):
                     # renamed file
                     k0 = os.path.join(self.root, prefs.convertToNativePath(m['old_path'][0]))
                     k1 = os.path.join(self.root, prefs.convertToNativePath(p))
diff --git a/src/vcs/rcs.py b/src/vcs/rcs.py
index e8ed73c..f75a7ab 100644
--- a/src/vcs/rcs.py
+++ b/src/vcs/rcs.py
@@ -25,7 +25,12 @@ from diffuse.vcs.vcs_interface import VcsInterface
 # RCS support
 class Rcs(VcsInterface):
     def getFileTemplate(self, prefs, name):
-        args = [ prefs.getString('rcs_bin_rlog'), '-L', '-h', utils.safeRelativePath(self.root, name, prefs, 'rcs_cygwin') ]
+        args = [
+            prefs.getString('rcs_bin_rlog'),
+            '-L',
+            '-h',
+            utils.safeRelativePath(self.root, name, prefs, 'rcs_cygwin')
+        ]
         rev = ''
         for line in utils.popenReadLines(self.root, args, prefs, 'rcs_bash'):
             if line.startswith('head: '):
@@ -69,12 +74,12 @@ class Rcs(VcsInterface):
                     recurse = os.path.isdir(os.path.join(s, 'RCS'))
                     if ex or recurse:
                         ex = False
-                        for v in os.listdir(s):
-                            dn = os.path.join(s, v)
-                            if v.endswith(',v') and os.path.isfile(dn):
+                        for d in os.listdir(s):
+                            dn = os.path.join(s, d)
+                            if d.endswith(',v') and os.path.isfile(dn):
                                 # map to checkout name
                                 r.append(dn[:-2])
-                            elif v == 'RCS' and os.path.isdir(dn):
+                            elif d == 'RCS' and os.path.isdir(dn):
                                 for v in os.listdir(dn):
                                     if os.path.isfile(os.path.join(dn, v)):
                                         if v.endswith(',v'):
diff --git a/src/vcs/svk.py b/src/vcs/svk.py
index 4ee1696..1e021c1 100644
--- a/src/vcs/svk.py
+++ b/src/vcs/svk.py
@@ -18,7 +18,6 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 import os
-import glob
 
 from diffuse import utils
 from diffuse.vcs.svn import Svn
@@ -32,7 +31,7 @@ class Svk(Svn):
 
     def _parseStatusLine(self, s):
         if len(s) < 4 or s[0] not in 'ACDMR':
-            return
+            return '', ''
         return s[0], s[4:]
 
     def _getPreviousRevision(self, rev):
@@ -43,6 +42,7 @@ class Svk(Svn):
         return str(int(rev) - 1)
 
     def getRevision(self, prefs, name, rev):
+        relpath = utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/')
         return utils.popenRead(
             self.root,
             [
@@ -50,9 +50,7 @@ class Svk(Svn):
                 'cat',
                 '-r',
                 rev,
-                '{}/{}'.format(
-                    self._getURL(prefs),
-                    utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/'))
+                f'{self._getURL(prefs)}/{relpath}'
             ],
             prefs,
             'svk_bash')
diff --git a/src/vcs/svn.py b/src/vcs/svn.py
index b6d3ca7..339d0a5 100644
--- a/src/vcs/svn.py
+++ b/src/vcs/svn.py
@@ -39,7 +39,7 @@ class Svn(VcsInterface):
 
     def _parseStatusLine(self, s):
         if len(s) < 8 or s[0] not in 'ACDMR':
-            return
+            return '', ''
         # subversion 1.6 adds a new column
         k = 7
         if k < len(s) and s[k] == ' ':
@@ -50,8 +50,7 @@ class Svn(VcsInterface):
         if rev is None:
             return 'BASE'
         m = int(rev)
-        if m > 1:
-            return str(m - 1)
+        return str(max(m > 1, 0))
 
     def _getURL(self, prefs):
         if self.url is None:
@@ -152,7 +151,7 @@ class Svn(VcsInterface):
                     m[d] = set()
                 m[d].add(b)
             # remove items we can easily determine to be directories
-            for k in m.keys():
+            for k in m:
                 d = os.path.dirname(k)
                 if d in m:
                     m[d].discard(os.path.basename(k))
@@ -161,7 +160,18 @@ class Svn(VcsInterface):
             # determine which are directories
             added = {}
             for p, v in m.items():
-                for s in utils.popenReadLines(self.root, [ vcs_bin, 'list', '-r', rev, '{}/{}'.format(self._getURL(prefs), p.replace(os.sep, '/')) ], prefs, vcs_bash):
+                lines = utils.popenReadLines(
+                    self.root,
+                    [
+                        vcs_bin,
+                        'list',
+                        '-r',
+                        rev,
+                        f"{self._getURL(prefs)}/{p.replace(os.sep, '/')}"
+                    ],
+                    prefs,
+                    vcs_bash)
+                for s in lines:
                     if s in v:
                         # confirmed as added file
                         k = os.path.join(self.root, os.path.join(p, s))
@@ -187,7 +197,18 @@ class Svn(VcsInterface):
                 m[d].add(b)
             removed_dir, removed = set(), {}
             for p, v in m.items():
-                for s in utils.popenReadLines(self.root, [ vcs_bin, 'list', '-r', prev, '{}/{}'.format(self._getURL(prefs), p.replace(os.sep, '/')) ], prefs, vcs_bash):
+                lines = utils.popenReadLines(
+                    self.root,
+                    [
+                        vcs_bin,
+                        'list',
+                        '-r',
+                        prev,
+                        f"{self._getURL(prefs)}/{p.replace(os.sep, '/')}"
+                    ],
+                    prefs,
+                    vcs_bash)
+                for s in lines:
                     if s.endswith('/'):
                         s = s[:-1]
                         if s in v:
@@ -205,7 +226,18 @@ class Svn(VcsInterface):
                 tmp = removed_dir
                 removed_dir = set()
                 for p in tmp:
-                    for s in utils.popenReadLines(self.root, [ vcs_bin, 'list', '-r', prev, '{}/{}'.format(self._getURL(prefs), p.replace(os.sep, '/')) ], prefs, vcs_bash):
+                    lines = utils.popenReadLines(
+                        self.root,
+                        [
+                            vcs_bin,
+                            'list',
+                            '-r',
+                            prev,
+                            f"{self._getURL(prefs)}/{p.replace(os.sep, '/')}"
+                        ],
+                        prefs,
+                        vcs_bash)
+                    for s in lines:
                         if s.endswith('/'):
                             # confirmed item as directory
                             removed_dir.add(os.path.join(p, s[:-1]))
@@ -239,7 +271,7 @@ class Svn(VcsInterface):
                 [
                     vcs_bin,
                     'cat',
-                    '{}@{}'.format(utils.safeRelativePath(self.root, name, prefs, 'svn_cygwin'), rev)
+                    f"{utils.safeRelativePath(self.root, name, prefs, 'svn_cygwin')}@{rev}"
                 ],
                 prefs,
                 'svn_bash')
@@ -248,10 +280,10 @@ class Svn(VcsInterface):
             [
                 vcs_bin,
                 'cat',
-                '{}/{}@{}'.format(
-                    self._getURL(prefs),
-                    utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/'),
-                    rev)
+                (
+                    f"{self._getURL(prefs)}/"
+                    f"{utils.relpath(self.root, os.path.abspath(name)).replace(os.sep, '/')}@{rev}"
+                )
             ],
             prefs,
             'svn_bash')
diff --git a/src/vcs/vcs_interface.py b/src/vcs/vcs_interface.py
index 16b57a0..c2b2b15 100644
--- a/src/vcs/vcs_interface.py
+++ b/src/vcs/vcs_interface.py
@@ -18,22 +18,21 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 class VcsInterface:
+    """Interface for the VCSs."""
+
     def __init__(self, root):
         """The object will initialized with the repository's root folder."""
-
         self.root = root
 
     def getFileTemplate(self, prefs, name):
-        """Indicates which revisions to display for a file when none were explicitly requested."""
-        pass
+        """Indicates which revisions to display for a file when none were explicitly
+           requested."""
 
     def getCommitTemplate(self, prefs, rev, names):
         """Indicates which file revisions to display for a commit."""
-        pass
 
     def getFolderTemplate(self, prefs, names):
         """Indicates which file revisions to display for a set of folders."""
 
     def getRevision(self, prefs, name, rev):
         """Returns the contents of the specified file revision"""
-        pass
diff --git a/src/vcs/vcs_registry.py b/src/vcs/vcs_registry.py
index ac17175..a08b792 100644
--- a/src/vcs/vcs_registry.py
+++ b/src/vcs/vcs_registry.py
@@ -46,9 +46,6 @@ class VcsRegistry:
             'svn': _get_svn_repo
         }
 
-    def setSearchOrder(self, ordering):
-        self._search_order = ordering
-
     # determines which VCS to use for files in the named folder
     def findByFolder(self, path, prefs):
         path = os.path.abspath(path)
@@ -57,11 +54,13 @@ class VcsRegistry:
                 repo = self._get_repo[vcs](path, prefs)
                 if repo:
                     return repo
+        return None
 
     # determines which VCS to use for the named file
     def findByFilename(self, name, prefs):
         if name is not None:
             return self.findByFolder(os.path.dirname(name), prefs)
+        return None
 
 
 # utility method to help find folders used by version control systems
@@ -77,29 +76,34 @@ def _find_parent_dir_with(path, dir_name):
 
 def _get_bzr_repo(path, prefs):
     p = _find_parent_dir_with(path, '.bzr')
-    if p:
-        return Bzr(p)
+    return Bzr(p) if p else None
 
 def _get_cvs_repo(path, prefs):
-    if os.path.isdir(os.path.join(path, 'CVS')):
-        return Cvs(path)
+    return Cvs(path) if os.path.isdir(os.path.join(path, 'CVS')) else None
 
 def _get_darcs_repo(path, prefs):
     p = _find_parent_dir_with(path, '_darcs')
-    if p:
-        return Darcs(p)
+    return Darcs(p) if p else None
 
 def _get_git_repo(path, prefs):
     if 'GIT_DIR' in os.environ:
         try:
             d = path
-            ss = utils.popenReadLines(d, [ prefs.getString('git_bin'), 'rev-parse', '--show-prefix' ], prefs, 'git_bash')
+            ss = utils.popenReadLines(
+                d,
+                [
+                    prefs.getString('git_bin'),
+                    'rev-parse',
+                    '--show-prefix'
+                ],
+                prefs,
+                'git_bash')
             if len(ss) > 0:
                 # be careful to handle trailing slashes
                 d = d.split(os.sep)
                 if d[-1] != '':
                     d.append('')
-                ss = strip_eol(ss[0]).split('/')
+                ss = utils.strip_eol(ss[0]).split('/')
                 if ss[-1] != '':
                     ss.append('')
                 n = len(ss)
@@ -110,7 +114,7 @@ def _get_git_repo(path, prefs):
                 else:
                     d = os.sep.join(d)
             return Git(d)
-        except (IOError, OSError, WindowsError):
+        except (IOError, OSError):
             # working tree not found
             pass
     # search for .git directory (project) or .git file (submodule)
@@ -125,13 +129,11 @@ def _get_git_repo(path, prefs):
 
 def _get_hg_repo(path, prefs):
     p = _find_parent_dir_with(path, '.hg')
-    if p:
-        return Hg(p)
+    return Hg(p) if p else None
 
 def _get_mtn_repo(path, prefs):
     p = _find_parent_dir_with(path, '_MTN')
-    if p:
-        return Mtn(p)
+    return Mtn(p) if p else None
 
 def _get_rcs_repo(path, prefs):
     if os.path.isdir(os.path.join(path, 'RCS')):
@@ -147,11 +149,11 @@ def _get_rcs_repo(path, prefs):
     except OSError:
         # the user specified an invalid folder name
         pass
+    return None
 
 def _get_svn_repo(path, prefs):
     p = _find_parent_dir_with(path, '.svn')
-    if p:
-        return Svn(p)
+    return Svn(p) if p else None
 
 def _get_svk_repo(path, prefs):
     name = path
@@ -166,9 +168,8 @@ def _get_svk_repo(path, prefs):
     if os.path.isfile(svkconfig):
         try:
             # find working copies by parsing the config file
-            f = open(svkconfig, 'r')
-            ss = readlines(f)
-            f.close()
+            with open(svkconfig, 'r', encoding='utf-8') as f:
+                ss = utils.readlines(f)
             projs, sep = [], os.sep
             # find the separator character
             for s in ss:
@@ -183,7 +184,11 @@ def _get_svk_repo(path, prefs):
                     while i < len(ss) and ss[i].startswith('    '):
                         s = ss[i]
                         i += 1
-                        if s.endswith(': ') and i < len(ss) and ss[i].startswith('      depotpath: '):
+                        if (
+                            s.endswith(': ') and
+                            i < len(ss) and
+                            ss[i].startswith('      depotpath: ')
+                        ):
                             key = s[4:-2].replace(sep, os.sep)
                             # parse directory path
                             j, n, tt = 0, len(key), []
@@ -195,7 +200,7 @@ def _get_svk_repo(path, prefs):
                                         if key[j] == '"':
                                             j += 1
                                             break
-                                        elif key[j] == '\\':
+                                        if key[j] == '\\':
                                             # escaped character
                                             j += 1
                                         if j < n:
@@ -214,3 +219,4 @@ def _get_svk_repo(path, prefs):
                 return Svk(path)
         except IOError:
             utils.logError(_('Error parsing %s.') % (svkconfig, ))
+    return None