Differential Revision: https://phabricator.services.mozilla.com/D162758

Differential Revision: https://phabricator.services.mozilla.com/D131254

Used to control auto-formatting, at the moment limited to black.
The current fileset pattern matches all `.py` files in the `python/`
directory and no files in any `third_party` directory.

Differential Revision: https://phabricator.services.mozilla.com/D117014