Add more flake8 tests

[cclauss]

Now that we have run black and isort, most flake8 tests pass.

This PR makes minor changes so that flake8 tests all pass except one that is incompatible with black.

• https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#flake8

[lavigne958]

Thanks for this PR.

I just have a few questions.

[lavigne958]

Lgtm