add flake8 and config

.flake8

@@ -0,0 +1,131 @@
+[flake8]
+
+ignore =
+  T400,T484,T499  # can't prevent flake8-mypy from running, but we can ignore it
+  P209,  # is about @csrf_protect, we have @performs_writes instead
+  B001,  # Do not use bare except:, IG90 will catch this.
+  C407,  # unnecessary list comprehension; A generator only better than a list
+         # comprehension if we don't always need to iterate through all items in
+         # the generator (based on the use case).
+
+  # The following codes belong to pycodestyle, and overlap with black:
+  E101,  # indentation contains mixed spaces and tabs; is subset of TXT2 (Tab
+         # Literal).
+  E111,  # indentation is not a multiple of four
+  E112,  # expected an indented block
+  E113,  # unexpected indentation
+  E114,  # indentation is not a multiple of four (comment)
+  E115,  # expected an indented block (comment)
+  E116,  # unexpected indentation (comment)
+  E121,  # continuation line under-indented for hanging indent
+  E122,  # continuation line missing indentation or outdented
+  E123,  # closing bracket does not match indentation of opening bracket’s line
+  E124,  # closing bracket does not match visual indentation
+  E125,  # continuation line with same indent as next logical line
+  E126,  # continuation line over-indented for hanging indent
+  E127,  # continuation line over-indented for visual indent; is harmless
+         # (over-indent is visually unambiguous) and currently generates too
+         # many warnings for existing code.
+  E128,  # continuation line under-indented for visual indent
+  E129,  # visually indented line with same indent as next logical line
+  E131,  # continuation line unaligned for hanging indent
+  E133,  # closing bracket is missing indentation
+  E201,  # whitespace after ‘(‘
+  E202,  # whitespace before ‘)’
+  E203,  # whitespace before ‘:’; this warning is invalid for slices
+  E211,  # whitespace before ‘(‘
+  E221,  # multiple spaces before operator
+  E222,  # multiple spaces after operator
+  E223,  # tab before operator
+  E224,  # tab after operator
+  E225,  # missing whitespace around operator
+  E226,  # missing whitespace around arithmetic operator
+  E227,  # missing whitespace around bitwise or shift operator
+  E228,  # missing whitespace around modulo operator
+  E231,  # missing whitespace after ‘,’, ‘;’, or ‘:’
+  E241,  # multiple spaces after ‘,’
+  E242,  # tab after ‘,’
+  E251,  # unexpected spaces around keyword / parameter equals
+  E261,  # at least two spaces before inline comment
+  E262,  # inline comment should start with ‘# ‘
+  E265,  # block comment should start with ‘# ‘
+  E266,  # too many leading ‘#’ for block comment
+  E271,  # multiple spaces after keyword
+  E272,  # multiple spaces before keyword
+  E273,  # tab after keyword
+  E274,  # tab before keyword
+  E275,  # missing whitespace after keyword
+  E301,  # expected 1 blank line, found 0
+  E302,  # expected 2 blank lines, found 0
+  E303,  # too many blank lines (3)
+  E304,  # blank lines found after function decorator
+  E305,  # expected 2 blank lines after end of function or class
+  E306,  # expected 1 blank line before a nested definition
+  E401,  # multiple imports on one line
+  E402,  # module level import not at top of file; warns on imports coming after
+         # statements. There are important use cases like demandimport
+         # (https://fburl.com/demandimport) that require statements before
+         # imports.
+  E501,  # line too long (82 > 79 characters); is same as TXT3 (Line Too Long).
+  E502,  # the backslash is redundant between brackets
+  E701,  # multiple statements on one line (colon)
+  E702,  # multiple statements on one line (semicolon)
+  E703,  # statement ends with a semicolon
+  E704,  # multiple statements on one line (def)
+  # These are pycodestyle lints that black doesn't catch:
+  # E711,  # comparison to None should be ‘if cond is None:’
+  # E712,  # comparison to True should be ‘if cond is True:’ or ‘if cond:’
+  # E713,  # test for membership should be ‘not in’
+  # E714,  # test for object identity should be ‘is not’
+  # E721,  # do not compare types, use ‘isinstance()’
+  # E722,  # do not use bare except, specify exception instead
+  # E731,  # do not assign a lambda expression, use a def
+  # E741,  # do not use variables named ‘l’, ‘O’, or ‘I’
+  # E742,  # do not define classes named ‘l’, ‘O’, or ‘I’
+  # E743,  # do not define functions named ‘l’, ‘O’, or ‘I’
+  # I think these are internal to pycodestyle?
+  # E901,  # SyntaxError or IndentationError
+  # E902,  # IOError
+  W191,  # indentation contains tabs
+  W291,  # trailing whitespace; is same as TXT6 (Trailing Whitespace).
+  W292,  # no newline at end of file; is same as TXT4 (File Does Not End in
+         # Newline).
+  W293,  # blank line contains whitespace; is same as TXT6 (Trailing
+         # Whitespace).
+  W391,  # blank line at end of file; is same as TXT9 (Trailing Whitespace at
+         # End of File).
+  W503,  # line break before binary operator; binary operator in a new line is
+         # the standard
+  W504,  # line break after binary operator
+  W505,  # not part of PEP8; doc line too long (82 > 79 characters)
+  # These are pycodestyle lints that black doesn't catch:
+  # W601,  # .has_key() is deprecated, use ‘in’
+  # W602,  # deprecated form of raising exception
+  # W603,  # ‘<>’ is deprecated, use ‘!=’
+  # W604,  # backticks are deprecated, use ‘repr()’
+  # W605,  # invalid escape sequence ‘x’
+  # W606,  # ‘async’ and ‘await’ are reserved keywords starting with Python 3.7
+
+# We should've silenced all of Flake8's line-length related lints, in favor of
+# Black. However, let's just set this to a large value just to be safe, in case
+# we accidentally left in a line-length related lint rule. If we don't set
+# anything, it defaults to 79, which is also wrong.
+max-line-length = 999
+
+exclude =
+  # version control
+  .svn,
+  CVS,
+  .bzr,
+  .hg,
+  .git,
+  # caches and environment
+  __pycache__,
+  .tox,
+  .eggs,
+  *.egg,
+  # Thrift-generated files
+  ttypes.py
+
+max-complexity = 12
+

tox.ini

@@ -2,4 +2,8 @@
 envlist = py36, py37
 
 [testenv]
-commands = python -m unittest
+deps = flake8
+commands = 
+	python -m unittest
+	flake8
+