Add more pre-commit hooks (again)

[kurtmckee]

Now that the Python 2 PR has merged, this PR introduces the following changes:

• Black and pyupgrade pre-commit have been added
• The hooks have both been run, and changes applied

I'm going to leave a review comment on this PR because something caught my eye and needs to be double-checked by a core developer.

[alexprengere]

Applying Black is fine for me, I addressed your review comment, so I am going to merge. Thanks!