Replace pylint with pyflakes/flake8

pylint reports a lot of warnings, but many of them are false positive,
and it's difficult to configure it. It also seems that for some reason
the included config file is not working well with the latest version.

Update the documentation to recommend using pyflakes and flake8 instead
of pylint. Remove the pylint config and add a basic flake8 config with
minimum settings:

- Maximum line length 80 columns
- Ignore warnings about indentation (repo uses 2 rather than expected 4)
- Ignore warnings about import placement

In this commit no code cleanup is done, and it's expected that most of
the files will throw up quite a few warnings, at least for flake8. These
can be cleaned up in follow-up commits.

The existing pylint suppression comments are left as-is. These will be
helpful when cleaning up pyflakes warnings later.

Change-Id: I2f7cb4340266ed07cc973ca6483b8f09d66a765b

.flake8

@@ -0,0 +1,3 @@
+[flake8]
+max-line-length=80
+ignore=E111,E114,E402

.pylintrc

@@ -1,298 +0,0 @@
-# lint Python modules using external checkers.
-#
-# This is the main checker controling the other ones and the reports
-# generation. It is itself both a raw checker and an astng checker in order
-# to:
-# * handle message activation / deactivation at the module level
-# * handle some basic but necessary stats'data (number of classes, methods...)
-#
-[MASTER]
-
-# Specify a configuration file.
-#rcfile=
-
-# Python code to execute, usually for sys.path manipulation such as
-# pygtk.require().
-#init-hook=
-
-# Profiled execution.
-profile=no
-
-# Add <file or directory> to the black list. It should be a base name, not a
-# path. You may set this option multiple times.
-ignore=SVN
-
-# Pickle collected data for later comparisons.
-persistent=yes
-
-# Set the cache size for astng objects.
-cache-size=500
-
-# List of plugins (as comma separated values of python modules names) to load,
-# usually to register additional checkers.
-load-plugins=
-
-
-[MESSAGES CONTROL]
-
-# Enable only checker(s) with the given id(s). This option conflicts with the
-# disable-checker option
-#enable-checker=
-
-# Enable all checker(s) except those with the given id(s). This option
-# conflicts with the enable-checker option
-#disable-checker=
-
-# Enable all messages in the listed categories.
-#enable-msg-cat=
-
-# Disable all messages in the listed categories.
-#disable-msg-cat=
-
-# Enable the message(s) with the given id(s).
-enable=RP0004
-
-# Disable the message(s) with the given id(s).
-disable=C0326,R0903,R0912,R0913,R0914,R0915,W0141,C0111,C0103,W0603,W0703,R0911,C0301,C0302,R0902,R0904,W0142,W0212,E1101,E1103,R0201,W0201,W0122,W0232,RP0001,RP0003,RP0101,RP0002,RP0401,RP0701,RP0801,F0401,E0611,R0801,I0011
-
-[REPORTS]
-
-# set the output format. Available formats are text, parseable, colorized, msvs
-# (visual studio) and html
-output-format=text
-
-# Put messages in a separate file for each module / package specified on the
-# command line instead of printing them on stdout. Reports (if any) will be
-# written in a file name "pylint_global.[txt|html]".
-files-output=no
-
-# Tells whether to display a full report or only the messages
-reports=yes
-
-# 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
-# respectivly contain the number of errors / warnings messages and the total
-# number of statements analyzed. This is used by the global evaluation report
-# (R0004).
-evaluation=10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10)
-
-# Add a comment according to your evaluation note. This is used by the global
-# evaluation report (R0004).
-comment=no
-
-# checks for
-# * unused variables / imports
-# * undefined variables
-# * redefinition of variable from builtins or from an outer scope
-# * use of variable before assigment
-#
-[VARIABLES]
-
-# Tells whether we should check for unused import in __init__ files.
-init-import=no
-
-# A regular expression matching names used for dummy variables (i.e. not used).
-dummy-variables-rgx=_|dummy
-
-# List of additional names supposed to be defined in builtins. Remember that
-# you should avoid to define new builtins when possible.
-additional-builtins=
-
-
-# try to find bugs in the code using type inference
-#
-[TYPECHECK]
-
-# 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
-
-# List of classes names for which member attributes should not be checked
-# (useful for classes with attributes dynamicaly set).
-ignored-classes=SQLObject
-
-# When zope mode is activated, consider the acquired-members option to ignore
-# access to some undefined attributes.
-zope=no
-
-# List of members which are usually get through zope's acquisition mecanism and
-# so shouldn't trigger E0201 when accessed (need zope=yes to be considered).
-acquired-members=REQUEST,acl_users,aq_parent
-
-
-# checks for :
-# * doc strings
-# * modules / classes / functions / methods / arguments / variables name
-# * number of arguments, local variables, branchs, returns and statements in
-# functions, methods
-# * required module attributes
-# * dangerous default values as arguments
-# * redefinition of function / method / class
-# * uses of the global statement
-#
-[BASIC]
-
-# Required attributes for module, separated by a comma
-required-attributes=
-
-# Regular expression which should only match functions or classes name which do
-# not require a docstring
-no-docstring-rgx=_main|__.*__
-
-# Regular expression which should only match correct module names
-module-rgx=(([a-z_][a-z0-9_]*)|([A-Z][a-zA-Z0-9]+))$
-
-# Regular expression which should only match correct module level names
-const-rgx=(([A-Z_][A-Z1-9_]*)|(__.*__))|(log)$
-
-# Regular expression which should only match correct class names
-class-rgx=[A-Z_][a-zA-Z0-9]+$
-
-# Regular expression which should only match correct function names
-function-rgx=[a-z_][a-z0-9_]{2,30}$
-
-# Regular expression which should only match correct method names
-method-rgx=[a-z_][a-z0-9_]{2,30}$
-
-# Regular expression which should only match correct instance attribute names
-attr-rgx=[a-z_][a-z0-9_]{2,30}$
-
-# Regular expression which should only match correct argument names
-argument-rgx=[a-z_][a-z0-9_]{2,30}$
-
-# Regular expression which should only match correct variable names
-variable-rgx=[a-z_][a-z0-9_]{2,30}$
-
-# Regular expression which should only match correct list comprehension /
-# generator expression variable names
-inlinevar-rgx=[A-Za-z_][A-Za-z0-9_]*$
-
-# Good variable names which should always be accepted, separated by a comma
-good-names=i,j,k,ex,Run,_,e,d1,d2,v,f,l,d
-
-# Bad variable names which should always be refused, separated by a comma
-bad-names=foo,bar,baz,toto,tutu,tata
-
-# List of builtins function names that should not be used, separated by a comma
-bad-functions=map,filter,apply,input
-
-
-# checks for sign of poor/misdesign:
-# * number of methods, attributes, local variables...
-# * size, complexity of functions, methods
-#
-[DESIGN]
-
-# Maximum number of arguments for function / method
-max-args=5
-
-# Maximum number of locals for function / method body
-max-locals=15
-
-# Maximum number of return / yield for function / method body
-max-returns=6
-
-# Maximum number of branch for function / method body
-max-branchs=12
-
-# Maximum number of statements in function / method body
-max-statements=50
-
-# Maximum number of parents for a class (see R0901).
-max-parents=7
-
-# Maximum number of attributes for a class (see R0902).
-max-attributes=20
-
-# Minimum number of public methods for a class (see R0903).
-min-public-methods=2
-
-# Maximum number of public methods for a class (see R0904).
-max-public-methods=30
-
-
-# checks for
-# * external modules dependencies
-# * relative / wildcard imports
-# * cyclic imports
-# * uses of deprecated modules
-#
-[IMPORTS]
-
-# Deprecated modules which should not be used, separated by a comma
-deprecated-modules=regsub,string,TERMIOS,Bastion,rexec
-
-# Create a graph of every (i.e. internal and external) dependencies in the
-# given file (report R0402 must not be disabled)
-import-graph=
-
-# Create a graph of external dependencies in the given file (report R0402 must
-# not be disabled)
-ext-import-graph=
-
-# Create a graph of internal dependencies in the given file (report R0402 must
-# not be disabled)
-int-import-graph=
-
-
-# checks for :
-# * methods without self as first argument
-# * overridden methods signature
-# * access only to existant members via self
-# * attributes not defined in the __init__ method
-# * supported interfaces implementation
-# * unreachable code
-#
-[CLASSES]
-
-# List of interface methods to ignore, separated by a comma. This is used for
-# instance to not check methods defines in Zope's Interface base class.
-ignore-iface-methods=isImplementedBy,deferred,extends,names,namesAndDescriptions,queryDescriptionFor,getBases,getDescriptionFor,getDoc,getName,getTaggedValue,getTaggedValueTags,isEqualOrExtendedBy,setTaggedValue,isImplementedByInstancesOf,adaptWith,is_implemented_by
-
-# List of method names used to declare (i.e. assign) instance attributes.
-defining-attr-methods=__init__,__new__,setUp
-
-
-# checks for similarities and duplicated code. This computation may be
-# memory / CPU intensive, so you should disable it if you experiments some
-# problems.
-#
-[SIMILARITIES]
-
-# Minimum lines number of a similarity.
-min-similarity-lines=4
-
-# Ignore comments when computing similarities.
-ignore-comments=yes
-
-# Ignore docstrings when computing similarities.
-ignore-docstrings=yes
-
-
-# checks for:
-# * warning notes in the code like FIXME, XXX
-# * PEP 263: source code with non ascii character but no encoding declaration
-#
-[MISCELLANEOUS]
-
-# List of note tags to take in consideration, separated by a comma.
-notes=FIXME,XXX,TODO
-
-
-# checks for :
-# * unauthorized constructions
-# * strict indentation
-# * line length
-# * use of <> instead of !=
-#
-[FORMAT]
-
-# Maximum number of characters on a single line.
-max-line-length=80
-
-# Maximum number of lines in a module
-max-module-lines=1000
-
-# String used as indentation unit. This is usually "    " (4 spaces) or "\t" (1
-# tab).  In repo it is 2 spaces.
-indent-string='  '

SUBMITTING_PATCHES.md

@@ -2,7 +2,7 @@
 
  - Make small logical changes.
  - Provide a meaningful commit message.
- - Check for coding errors with pylint
+ - Check for coding errors and style nits with pyflakes and flake8
  - Make sure all code is under the Apache License, 2.0.
  - Publish your changes for review.
  - Make corrections if requested.
@@ -36,12 +36,32 @@ If your description starts to get too long, that's a sign that you
 probably need to split up your commit to finer grained pieces.
 
 
-## Check for coding errors with pylint
+## Check for coding errors and style nits with pyflakes and flake8
 
-Run pylint on changed modules using the provided configuration:
+### Coding errors
 
-    pylint --rcfile=.pylintrc file.py
+Run `pyflakes` on changed modules:
 
+    pyflakes file.py
+
+Ideally there should be no new errors or warnings introduced.
+
+### Style violations
+
+Run `flake8` on changes modules:
+
+    flake8 file.py
+
+Note that repo generally follows [Google's python style guide]
+(https://google.github.io/styleguide/pyguide.html) rather than [PEP 8]
+(https://www.python.org/dev/peps/pep-0008/), so it's possible that
+the output of `flake8` will be quite noisy. It's not mandatory to
+avoid all warnings, but at least the maximum line length should be
+followed.
+
+If there are many occurrences of the same warning that cannot be
+avoided without going against the Google style guide, these may be
+suppressed in the included `.flake8` file.
 
 ## Check the license