Change linter from pep8 to flake8
From the pypi project page:
Flake8 is a wrapper around these tools:
- Ned Batchelder’s McCabe script
pycodestyle is what was former called pep8
So flake8 does some more linting. It also found some issues the old pep8 linter didn't find.
These new lint issues are also fixed with this diff.
Test Plan: n/A
Reviewers: WyldBot, CLOVIS
Reviewed By: WyldBot
Differential Revision: https://phabricator.wildfyre.net/D232