Merge remote-tracking branch 'origin/pr/2470' into mbedtls-2.16

* origin/pr/2470:
  Silence pylint
  check-files.py: readability improvement in permission check
  check-files.py: use class fields for class-wide constants
  check-files.py: clean up class structure
  abi_check.py: Document more methods
  check-files.py: document some classes and methods
  Fix pylint errors going uncaught
  Call pylint3, not pylint
  New, documented pylint configuration

9 files changed, 178 insertions, 508 deletions

diff --git a/.pylint b/.pylint
deleted file mode 100644
index 934f30be..00000000
--- a/.pylint
+++ /dev/null
@@ -1,425 +0,0 @@
-[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-whitelist=
-
-# Add files or directories to the blacklist. They should be base names, not
-# paths.
-ignore=CVS
-
-# Add files or directories matching the regex patterns to the blacklist. 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.
-jobs=1
-
-# List of plugins (as comma separated values of python modules names) to load,
-# usually to register additional checkers.
-load-plugins=
-
-# Pickle collected data for later comparisons.
-persistent=yes
-
-# Specify a configuration file.
-#rcfile=
-
-# 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=print-statement,parameter-unpacking,unpacking-in-except,old-raise-syntax,backtick,long-suffix,old-ne-operator,old-octal-literal,import-star-module-level,raw-checker-failed,bad-inline-option,locally-disabled,locally-enabled,file-ignored,suppressed-message,useless-suppression,deprecated-pragma,apply-builtin,basestring-builtin,buffer-builtin,cmp-builtin,coerce-builtin,execfile-builtin,file-builtin,long-builtin,raw_input-builtin,reduce-builtin,standarderror-builtin,unicode-builtin,xrange-builtin,coerce-method,delslice-method,getslice-method,setslice-method,no-absolute-import,old-division,dict-iter-method,dict-view-method,next-method-called,metaclass-assignment,indexing-exception,raising-string,reload-builtin,oct-method,hex-method,nonzero-method,cmp-method,input-builtin,round-builtin,intern-builtin,unichr-builtin,map-builtin-not-iterating,zip-builtin-not-iterating,range-builtin-not-iterating,filter-builtin-not-iterating,using-cmp-argument,eq-without-hash,div-method,idiv-method,rdiv-method,exception-message-attribute,invalid-str-codec,sys-max-int,bad-python3-import,deprecated-string-function,deprecated-str-translate-call
-
-# 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=
-
-
-[REPORTS]
-
-# Python expression which should return a note less than 10 (10 is the highest
-# note). You have access to the variables errors warning, statement which
-# respectively contain the number of errors / warnings messages and the total
-# number of statements analyzed. This 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, eg
-# 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
-
-
-[SIMILARITIES]
-
-# Ignore comments when computing similarities.
-ignore-comments=yes
-
-# Ignore docstrings when computing similarities.
-ignore-docstrings=yes
-
-# Ignore imports when computing similarities.
-ignore-imports=no
-
-# Minimum lines number of a similarity.
-min-similarity-lines=4
-
-
-[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=79
-
-# Maximum number of lines in a module
-max-module-lines=2000
-
-# List of optional constructs for which whitespace checking is disabled. `dict-
-# separator` is used to allow tabulation in dicts, etc.: {1  : 1,\n222: 2}.
-# `trailing-comma` allows a space between comma and closing bracket: (a, ).
-# `empty-line` allows space-only lines.
-no-space-check=trailing-comma,dict-separator
-
-# 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
-
-
-[BASIC]
-
-# Naming hint for argument names
-argument-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Regular expression matching correct argument names
-argument-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Naming hint for attribute names
-attr-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Regular expression matching correct attribute names
-attr-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Bad variable names which should always be refused, separated by a comma
-bad-names=foo,bar,baz,toto,tutu,tata
-
-# Naming hint for class attribute names
-class-attribute-name-hint=([A-Za-z_][A-Za-z0-9_]{2,30}|(__.*__))$
-
-# Regular expression matching correct class attribute names
-class-attribute-rgx=([A-Za-z_][A-Za-z0-9_]{2,30}|(__.*__))$
-
-# Naming hint for class names
-class-name-hint=[A-Z_][a-zA-Z0-9]+$
-
-# Regular expression matching correct class names
-class-rgx=[A-Z_][a-zA-Z0-9]+$
-
-# Naming hint for constant names
-const-name-hint=(([A-Z_][A-Z0-9_]*)|(__.*__))$
-
-# Regular expression matching correct constant names
-const-rgx=(([A-Z_][A-Z0-9_]*)|(__.*__))$
-
-# Minimum line length for functions/classes that require docstrings, shorter
-# ones are exempt.
-docstring-min-length=-1
-
-# Naming hint for function names
-function-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Regular expression matching correct function names
-function-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Good variable names which should always be accepted, separated by a comma
-good-names=i,j,k,ex,Run,_
-
-# Include a hint for the correct naming format with invalid-name
-include-naming-hint=no
-
-# Naming hint for inline iteration names
-inlinevar-name-hint=[A-Za-z_][A-Za-z0-9_]*$
-
-# Regular expression matching correct inline iteration names
-inlinevar-rgx=[A-Za-z_][A-Za-z0-9_]*$
-
-# Naming hint for method names
-method-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Regular expression matching correct method names
-method-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Naming hint for module names
-module-name-hint=(([a-z_][a-z0-9_]*)|([A-Z][a-zA-Z0-9]+))$
-
-# Regular expression matching correct module names
-module-rgx=(([a-z_][a-z0-9_]*)|([A-Z][a-zA-Z0-9]+))$
-
-# 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.
-property-classes=abc.abstractproperty
-
-# Naming hint for variable names
-variable-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-# Regular expression matching correct variable names
-variable-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
-
-
-[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
-
-# 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
-
-
-[VARIABLES]
-
-# List of additional names supposed to be defined in builtins. Remember that
-# you should avoid to define new builtins when possible.
-additional-builtins=
-
-# Tells whether unused global variables should be treated as a violation.
-allow-global-unused-variables=yes
-
-# 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. expectedly
-# not 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,future.builtins
-
-
-[SPELLING]
-
-# Spelling dictionary name. Available dictionaries: none. To make it working
-# install python-enchant package.
-spelling-dict=
-
-# List of comma separated words that should not be checked.
-spelling-ignore-words=
-
-# A path to a file that contains private dictionary; one word per line.
-spelling-private-dict-file=
-
-# Tells whether to store unknown words to indicated private dictionary in
-# --spelling-private-dict-file option instead of raising a message.
-spelling-store-unknown-words=no
-
-
-[MISCELLANEOUS]
-
-# List of note tags to take in consideration, separated by a comma.
-notes=FIXME,XXX,TODO
-
-
-[LOGGING]
-
-# Logging modules to check that the string format arguments are in logging
-# function parameter format
-logging-modules=logging
-
-
-[CLASSES]
-
-# List of method names used to declare (i.e. assign) instance attributes.
-defining-attr-methods=__init__,__new__,setUp
-
-# 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=mcs
-
-
-[DESIGN]
-
-# 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 a if statement
-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]
-
-# 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=regsub,TERMIOS,Bastion,rexec
-
-# Create a graph of external dependencies in the given file (report RP0402 must
-# not be disabled)
-ext-import-graph=
-
-# Create a graph of every (i.e. internal and external) dependencies in the
-# given file (report RP0402 must not be disabled)
-import-graph=
-
-# Create a graph of internal dependencies in 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
-
-
-[EXCEPTIONS]
-
-# Exceptions that will emit a warning when being caught. Defaults to
-# "Exception"
-overgeneral-exceptions=Exception
diff --git a/.pylintrc b/.pylintrc
new file mode 100644
index 00000000..168e0b75
--- /dev/null
+++ b/.pylintrc
@@ -0,0 +1,52 @@
+[BASIC]
+# We're ok with short funtion argument names.
+# [invalid-name]
+argument-rgx=[a-z_][a-z0-9_]*$
+
+# Allow filter and map.
+# [bad-builtin]
+bad-functions=input
+
+# We prefer docstrings, but we don't require them on all functions.
+# Require them only on long functions (for some value of long).
+# [missing-docstring]
+docstring-min-length=10
+
+# Allow longer methods than the default.
+# [invalid-name]
+method-rgx=[a-z_][a-z0-9_]{2,35}$
+
+# Allow module names containing a dash (but no underscore or uppercase letter).
+# They are whole programs, not meant to be included by another module.
+# [invalid-name]
+module-rgx=(([a-z_][a-z0-9_]*)|([A-Z][a-zA-Z0-9]+)|[a-z][-0-9a-z]+)$
+
+# Some functions don't need docstrings.
+# [missing-docstring]
+no-docstring-rgx=(run_)main$
+
+# We're ok with short local or global variable names.
+# [invalid-name]
+variable-rgx=[a-z_][a-z0-9_]*$
+
+[DESIGN]
+# Allow more than the default 7 attributes.
+# [too-many-instance-attributes]
+max-attributes=15
+
+[FORMAT]
+# Allow longer modules than the default recommended maximum.
+# [too-many-lines]
+max-module-lines=2000
+
+[MESSAGES CONTROL]
+disable=
+
+[REPORTS]
+# Don't diplay statistics. Just the facts.
+reports=no
+
+[VARIABLES]
+# Allow unused variables if their name starts with an underscore.
+# [unused-argument]
+dummy-variables-rgx=_.*
diff --git a/scripts/abi_check.py b/scripts/abi_check.py
index 8f9cd0f4..2a90b68f 100755
--- a/scripts/abi_check.py
+++ b/scripts/abi_check.py
@@ -26,8 +26,16 @@ import tempfile
 
 
 class AbiChecker(object):
+    """API and ABI checker."""
 
     def __init__(self, report_dir, old_rev, new_rev, keep_all_reports):
+        """Instantiate the API/ABI checker.
+
+        report_dir: directory for output files
+        old_rev: reference git revision to compare against
+        new_rev: git revision to check
+        keep_all_reports: if false, delete old reports
+        """
         self.repo_path = "."
         self.log = None
         self.setup_logger()
@@ -42,7 +50,8 @@ class AbiChecker(object):
         self.git_command = "git"
         self.make_command = "make"
 
-    def check_repo_path(self):
+    @staticmethod
+    def check_repo_path():
         current_dir = os.path.realpath('.')
         root_dir = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
         if current_dir != root_dir:
@@ -53,12 +62,15 @@ class AbiChecker(object):
         self.log.setLevel(logging.INFO)
         self.log.addHandler(logging.StreamHandler())
 
-    def check_abi_tools_are_installed(self):
+    @staticmethod
+    def check_abi_tools_are_installed():
         for command in ["abi-dumper", "abi-compliance-checker"]:
             if not shutil.which(command):
                 raise Exception("{} not installed, aborting".format(command))
 
     def get_clean_worktree_for_git_revision(self, git_rev):
+        """Make a separate worktree with git_rev checked out.
+        Do not modify the current worktree."""
         self.log.info(
             "Checking out git worktree for revision {}".format(git_rev)
         )
@@ -76,6 +88,7 @@ class AbiChecker(object):
         return git_worktree_path
 
     def build_shared_libraries(self, git_worktree_path):
+        """Build the shared libraries in the specified worktree."""
         my_environment = os.environ.copy()
         my_environment["CFLAGS"] = "-g -Og"
         my_environment["SHARED"] = "1"
@@ -92,6 +105,9 @@ class AbiChecker(object):
             raise Exception("make failed, aborting")
 
     def get_abi_dumps_from_shared_libraries(self, git_ref, git_worktree_path):
+        """Generate the ABI dumps for the specified git revision.
+        It must be checked out in git_worktree_path and the shared libraries
+        must have been built."""
         abi_dumps = {}
         for mbed_module in self.mbedtls_modules:
             output_path = os.path.join(
@@ -117,6 +133,7 @@ class AbiChecker(object):
         return abi_dumps
 
     def cleanup_worktree(self, git_worktree_path):
+        """Remove the specified git worktree."""
         shutil.rmtree(git_worktree_path)
         worktree_process = subprocess.Popen(
             [self.git_command, "worktree", "prune"],
@@ -130,6 +147,7 @@ class AbiChecker(object):
             raise Exception("Worktree cleanup failed, aborting")
 
     def get_abi_dump_for_ref(self, git_rev):
+        """Generate the ABI dumps for the specified git revision."""
         git_worktree_path = self.get_clean_worktree_for_git_revision(git_rev)
         self.build_shared_libraries(git_worktree_path)
         abi_dumps = self.get_abi_dumps_from_shared_libraries(
@@ -139,6 +157,9 @@ class AbiChecker(object):
         return abi_dumps
 
     def get_abi_compatibility_report(self):
+        """Generate a report of the differences between the reference ABI
+        and the new ABI. ABI dumps from self.old_rev and self.new_rev must
+        be available."""
         compatibility_report = ""
         compliance_return_code = 0
         for mbed_module in self.mbedtls_modules:
@@ -188,6 +209,8 @@ class AbiChecker(object):
         return compliance_return_code
 
     def check_for_abi_changes(self):
+        """Generate a report of ABI differences
+        between self.old_rev and self.new_rev."""
         self.check_repo_path()
         self.check_abi_tools_are_installed()
         self.old_dumps = self.get_abi_dump_for_ref(self.old_rev)
@@ -232,7 +255,9 @@ def run_main():
         )
         return_code = abi_check.check_for_abi_changes()
         sys.exit(return_code)
-    except Exception:
+    except Exception: # pylint: disable=broad-except
+        # Print the backtrace and exit explicitly so as to exit with
+        # status 2, not 1.
         traceback.print_exc()
         sys.exit(2)
 
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 53fbc7e2..a8d067b4 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -1247,6 +1247,9 @@ component_test_zeroize () {
     unset gdb_disable_aslr
 }
 
+support_check_python_files () {
+    type pylint3 >/dev/null 2>/dev/null
+}
 component_check_python_files () {
     msg "Lint: Python scripts"
     record_status tests/scripts/check-python-files.sh
diff --git a/tests/scripts/check-files.py b/tests/scripts/check-files.py
index 005a077c..00fd0edf 100755
--- a/tests/scripts/check-files.py
+++ b/tests/scripts/check-files.py
@@ -19,14 +19,23 @@ import codecs
 import sys
 
 
-class IssueTracker(object):
-    """Base class for issue tracking. Issues should inherit from this and
-    overwrite either issue_with_line if they check the file line by line, or
-    overwrite check_file_for_issue if they check the file as a whole."""
+class FileIssueTracker(object):
+    """Base class for file-wide issue tracking.
+
+    To implement a checker that processes a file as a whole, inherit from
+    this class and implement `check_file_for_issue` and define ``heading``.
+
+    ``files_exemptions``: files whose name ends with a string in this set
+     will not be checked.
+
+    ``heading``: human-readable description of the issue
+    """
+
+    files_exemptions = frozenset()
+    # heading must be defined in derived classes.
+    # pylint: disable=no-member
 
     def __init__(self):
-        self.heading = ""
-        self.files_exemptions = []
         self.files_with_issues = {}
 
     def should_check_file(self, filepath):
@@ -35,23 +44,14 @@ class IssueTracker(object):
                 return False
         return True
 
-    def issue_with_line(self, line):
-        raise NotImplementedError
-
     def check_file_for_issue(self, filepath):
-        with open(filepath, "rb") as f:
-            for i, line in enumerate(iter(f.readline, b"")):
-                self.check_file_line(filepath, line, i + 1)
+        raise NotImplementedError
 
     def record_issue(self, filepath, line_number):
         if filepath not in self.files_with_issues.keys():
             self.files_with_issues[filepath] = []
         self.files_with_issues[filepath].append(line_number)
 
-    def check_file_line(self, filepath, line, line_number):
-        if self.issue_with_line(line):
-            self.record_issue(filepath, line_number)
-
     def output_file_issues(self, logger):
         if self.files_with_issues.values():
             logger.info(self.heading)
@@ -64,24 +64,44 @@ class IssueTracker(object):
                     logger.info(filename)
             logger.info("")
 
+class LineIssueTracker(FileIssueTracker):
+    """Base class for line-by-line issue tracking.
 
-class PermissionIssueTracker(IssueTracker):
+    To implement a checker that processes files line by line, inherit from
+    this class and implement `line_with_issue`.
+    """
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "Incorrect permissions:"
+    def issue_with_line(self, line, filepath):
+        raise NotImplementedError
+
+    def check_file_line(self, filepath, line, line_number):
+        if self.issue_with_line(line, filepath):
+            self.record_issue(filepath, line_number)
+
+    def check_file_for_issue(self, filepath):
+        with open(filepath, "rb") as f:
+            for i, line in enumerate(iter(f.readline, b"")):
+                self.check_file_line(filepath, line, i + 1)
+
+class PermissionIssueTracker(FileIssueTracker):
+    """Track files with bad permissions.
+
+    Files that are not executable scripts must not be executable."""
+
+    heading = "Incorrect permissions:"
 
     def check_file_for_issue(self, filepath):
-        if not (os.access(filepath, os.X_OK) ==
-                filepath.endswith((".sh", ".pl", ".py"))):
+        is_executable = os.access(filepath, os.X_OK)
+        should_be_executable = filepath.endswith((".sh", ".pl", ".py"))
+        if is_executable != should_be_executable:
             self.files_with_issues[filepath] = None
 
 
-class EndOfFileNewlineIssueTracker(IssueTracker):
+class EndOfFileNewlineIssueTracker(FileIssueTracker):
+    """Track files that end with an incomplete line
+    (no newline character at the end of the last line)."""
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "Missing newline at end of file:"
+    heading = "Missing newline at end of file:"
 
     def check_file_for_issue(self, filepath):
         with open(filepath, "rb") as f:
@@ -89,11 +109,11 @@ class EndOfFileNewlineIssueTracker(IssueTracker):
                 self.files_with_issues[filepath] = None
 
 
-class Utf8BomIssueTracker(IssueTracker):
+class Utf8BomIssueTracker(FileIssueTracker):
+    """Track files that start with a UTF-8 BOM.
+    Files should be ASCII or UTF-8. Valid UTF-8 does not start with a BOM."""
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "UTF-8 BOM present:"
+    heading = "UTF-8 BOM present:"
 
     def check_file_for_issue(self, filepath):
         with open(filepath, "rb") as f:
@@ -101,79 +121,76 @@ class Utf8BomIssueTracker(IssueTracker):
                 self.files_with_issues[filepath] = None
 
 
-class LineEndingIssueTracker(IssueTracker):
+class LineEndingIssueTracker(LineIssueTracker):
+    """Track files with non-Unix line endings (i.e. files with CR)."""
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "Non Unix line endings:"
+    heading = "Non Unix line endings:"
 
-    def issue_with_line(self, line):
+    def issue_with_line(self, line, _filepath):
         return b"\r" in line
 
 
-class TrailingWhitespaceIssueTracker(IssueTracker):
+class TrailingWhitespaceIssueTracker(LineIssueTracker):
+    """Track lines with trailing whitespace."""
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "Trailing whitespace:"
-        self.files_exemptions = [".md"]
+    heading = "Trailing whitespace:"
+    files_exemptions = frozenset(".md")
 
-    def issue_with_line(self, line):
+    def issue_with_line(self, line, _filepath):
         return line.rstrip(b"\r\n") != line.rstrip()
 
 
-class TabIssueTracker(IssueTracker):
+class TabIssueTracker(LineIssueTracker):
+    """Track lines with tabs."""
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "Tabs present:"
-        self.files_exemptions = [
-            "Makefile", "generate_visualc_files.pl"
-        ]
+    heading = "Tabs present:"
+    files_exemptions = frozenset([
+        "Makefile",
+        "generate_visualc_files.pl",
+    ])
 
-    def issue_with_line(self, line):
+    def issue_with_line(self, line, _filepath):
         return b"\t" in line
 
 
-class MergeArtifactIssueTracker(IssueTracker):
+class MergeArtifactIssueTracker(LineIssueTracker):
+    """Track lines with merge artifacts.
+    These are leftovers from a ``git merge`` that wasn't fully edited."""
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "Merge artifact:"
+    heading = "Merge artifact:"
 
-    def issue_with_line(self, filepath, line):
+    def issue_with_line(self, line, _filepath):
         # Detect leftover git conflict markers.
         if line.startswith(b'<<<<<<< ') or line.startswith(b'>>>>>>> '):
             return True
         if line.startswith(b'||||||| '): # from merge.conflictStyle=diff3
             return True
         if line.rstrip(b'\r\n') == b'=======' and \
-           not filepath.endswith('.md'):
+           not _filepath.endswith('.md'):
             return True
         return False
 
-    def check_file_line(self, filepath, line, line_number):
-        if self.issue_with_line(filepath, line):
-            self.record_issue(filepath, line_number)
-
-class TodoIssueTracker(IssueTracker):
+class TodoIssueTracker(LineIssueTracker):
+    """Track lines containing ``TODO``."""
 
-    def __init__(self):
-        super().__init__()
-        self.heading = "TODO present:"
-        self.files_exemptions = [
-            os.path.basename(__file__),
-            "benchmark.c",
-            "pull_request_template.md",
-        ]
+    heading = "TODO present:"
+    files_exemptions = frozenset([
+        os.path.basename(__file__),
+        "benchmark.c",
+        "pull_request_template.md",
+    ])
 
-    def issue_with_line(self, line):
+    def issue_with_line(self, line, _filepath):
         return b"todo" in line.lower()
 
 
 class IntegrityChecker(object):
+    """Sanity-check files under the current directory."""
 
     def __init__(self, log_file):
+        """Instantiate the sanity checker.
+        Check files under the current directory.
+        Write a report of issues to log_file."""
         self.check_repo_path()
         self.logger = None
         self.setup_logger(log_file)
@@ -197,7 +214,8 @@ class IntegrityChecker(object):
             TodoIssueTracker(),
         ]
 
-    def check_repo_path(self):
+    @staticmethod
+    def check_repo_path():
         if not all(os.path.isdir(d) for d in ["include", "library", "tests"]):
             raise Exception("Must be run from Mbed TLS root")
 
diff --git a/tests/scripts/check-python-files.sh b/tests/scripts/check-python-files.sh
index 009ba4cb..92904182 100755
--- a/tests/scripts/check-python-files.sh
+++ b/tests/scripts/check-python-files.sh
@@ -9,10 +9,4 @@
 # Run 'pylint' on Python files for programming errors and helps enforcing
 # PEP8 coding standards.
 
-if `hash pylint > /dev/null 2>&1`; then
-    pylint -j 2 tests/scripts/generate_test_code.py --rcfile .pylint
-    pylint -j 2 tests/scripts/test_generate_test_code.py --rcfile .pylint
-    pylint -j 2 tests/scripts/mbedtls_test.py --rcfile .pylint
-else
-    echo "$0: WARNING: 'pylint' not found! Skipping checks on Python files."
-fi
+pylint3 -j 2 scripts/*.py tests/scripts/*.py
diff --git a/tests/scripts/generate_test_code.py b/tests/scripts/generate_test_code.py
index 12580244..1fff0999 100755
--- a/tests/scripts/generate_test_code.py
+++ b/tests/scripts/generate_test_code.py
@@ -238,7 +238,7 @@ class FileWrapper(io.FileIO, object):
         if hasattr(parent, '__next__'):
             line = parent.__next__()  # Python 3
         else:
-            line = parent.next()  # Python 2
+            line = parent.next()  # Python 2 # pylint: disable=no-member
         if line is not None:
             self._line_no += 1
             # Convert byte array to string with correct encoding and
diff --git a/tests/scripts/mbedtls_test.py b/tests/scripts/mbedtls_test.py
index c7027659..ac2912d4 100755
--- a/tests/scripts/mbedtls_test.py
+++ b/tests/scripts/mbedtls_test.py
@@ -37,7 +37,8 @@ https://github.com/ARMmbed/greentea
 import re
 import os
 import binascii
-from mbed_host_tests import BaseHostTest, event_callback
+
+from mbed_host_tests import BaseHostTest, event_callback # pylint: disable=import-error
 
 
 class TestDataParserError(Exception):
diff --git a/tests/scripts/test_generate_test_code.py b/tests/scripts/test_generate_test_code.py
index 2ef12e18..6d7113e1 100755
--- a/tests/scripts/test_generate_test_code.py
+++ b/tests/scripts/test_generate_test_code.py
@@ -22,7 +22,7 @@
 Unit tests for generate_test_code.py
 """
 
-
+# pylint: disable=wrong-import-order
 try:
     # Python 2
     from StringIO import StringIO
@@ -36,6 +36,7 @@ try:
 except ImportError:
     # Python 3
     from unittest.mock import patch
+# pylint: enable=wrong-import-order
 from generate_test_code import gen_dependencies, gen_dependencies_one_line
 from generate_test_code import gen_function_wrapper, gen_dispatch
 from generate_test_code import parse_until_pattern, GeneratorInputError
@@ -336,6 +337,7 @@ class StringIOWrapper(StringIO, object):
         :param length:
         :return:
         """
+        # pylint: disable=unused-argument
         line = super(StringIOWrapper, self).readline()
         if line is not None:
             self.line_no += 1