Add Black Python formatter/linter?

[pdehaan]

https://black.readthedocs.io/en/stable/installation_and_usage.html#usage

black . --exclude venv

Not sure how much linting for errors or issues Black does, or if it's mostly just a formatter (ESLint vs Prettier), so maybe we need to add other Python linting as well.

[groovecoder]

Do we use black in other python code-bases? I've always used flake8 for python code.

[pdehaan]

I've heard that we use it, but I'll ping my larger team and see if they can point me to any prior works of art.

I did find https://bugzilla.mozilla.org/show_bug.cgi?id=1555560 in my email records, but that doesn't look merged yet.

[jeroenev]

Do we use black in other python code-bases? I've always used flake8 for python code.

Black is mostly a Code formatter, making sure all code is formatted consistently across a project, kinda like Prettier for JS.
So it's for a different purpose than Flake8.

[groovecoder]

Closing this Black-specific issue for the more open-ended #162.