Stubs and examples can use linting

[IsaacG]

This is a superset of #2579 (long lines)

pylint flags all sorts of issues that ought to be cleaned up.

» find exercises -name \*.py ! -name \*_test.py -exec pylint -d C0116,W0613,C0114,C0115,C0103,R0801,W0707,W0107,C0301,R0903,W0511 {} +

Logging this is a "on hold, revisit later" type issue for now.

[BethanyG]

..and as a superset of #2579, it has a hold for a similar reason. We need to have the track a bit more stable and a bit more filled out with concepts and concept exercises before we loop back for a discussion about practice stub files, line length, or any PyLint whining. We may also choose to not enforce some PyLint rules. That is still TBD.

Additionally - example files are more or less exempt from formal linting rules. It isn't that "anything goes" -- but the spec says nothing about them being any sort of exemplar, and they are at most a "minimum implementation" for use in CI and testing. It is a very low priority that we look through them all.

[J08K]

Whoops, closed the wrong thing 💙

[J08K]

Closed by 8 PRs, linted all stubs and exemplars.