Iteratively enable flake8 checks

[StanczakDominik]

#1062 brought back flake8 linter checks, but kept most of them disabled. There are a bunch of them in setup.cfg:

PlasmaPy/setup.cfg

Lines 96 to 185 in 4a71ade

	[flake8]
	convention = numpy
	# Checks marked as TODO should be eventually enabled,
	# but are failing right now. These are *great*
	# first contributions. ;)
	# Checks not marked by TODO *maybe* should be
	# eventually enabled ― ask!
	extend-ignore =
	# TODO D100: Missing docstring in public module
	D100,
	# TODO D102: Missing docstring in public method
	D102,
	# TODO D103: Missing docstring in public function
	D103,
	# TODO D104: Missing docstring in public package
	D104,
	D105,
	D107,
	# TODO D200: One-line docstring should fit on one line with quotes
	D200,
	# Ignoring D202 allows blank lines to be put on either side of code "paragraphs" at the beginning of a function.
	D202,
	# D205 and D400 are ignored to allow the "one-liner" to exceed one
	# line, which is sometimes necessary for even concise descriptions of plasma
	# physics functions and classes.
	D205,
	# TODO D210: No whitespaces allowed surrounding docstring text
	D210,
	# TODO D301: Use r""" if any backslashes in a docstring
	D301,
	# D302 is unnecessary as we are using Python 3.6+.
	D302,
	# D205 and D400 are ignored to allow the "one-liner" to exceed one
	# line, which is sometimes necessary for even concise descriptions of plasma
	# physics functions and classes.
	D400,
	# TODO D401: First line should be in imperative mood
	D401,
	# D403: First word of the first line should be properly capitalized ('Latex', not 'LaTeX') # Dominik: good job, pydocstyle /s
	D403,
	# TODO D407: Missing dashed underline after section ('References')
	D407,
	# TODO D409: Section underline should match the length of its name (Expected 5 dashes in section 'Notes', got 10)
	D409,
	# TODO D412: No blank lines allowed between a section header and its content
	D412
	# E203 something something whitespace? TODO check again
	E203,
	E501,
	# TODO E712 comparison to False should be if cond is False or if not cond
	E712,
	# TODO E713 test for membership should be 'not in'
	E713,
	# E731 do not assign a lambda, use a def - Dominik: disagreed, lambdas have uses
	E731,
	F401,
	# TODO star imports and undefined variables
	F403,
	F405,
	# all TODO from here on out, probably
	F541,
	# W605 invalid escape sequence,
	W605,
	RST210,
	RST213,
	RST306,
	RST902,
	exclude =
	extern,
	sphinx,
	*test*,
	*parsetab.py,
	conftest.py,
	docs/conf.py,
	setup.py,
	.jupyter
	rst-roles =
	# TODO look into these
	attr,
	class,
	func,
	data,
	exc,
	file,
	meth,
	mod
	rst-directives =
	deprecated,
	nbgallery,
	todo

It'd be nice to have them back. This would mean, for any brave soul willing to undertake this, for every check marked as TODO (and probably some others, too):

• enable the check again by removing it from the exclude list;
• fix all the lint errors that flake8 (in the tests section) starts throwing at you;
• continue down the list for as long as you'd like.

This is, admittedly, not exciting, but quite helpful and simple to execute; would be great for a new contributor.

[aksalcido]

Hello Dominik, I emailed you and I would like to work on this :)

[StanczakDominik]

Go right ahead! 😄