Enforce code formatting repo-wide and add CI job

[dtasev]

Issue raised by: developer

What?

Currently there is no formatting style enforced. This can be annoying when you do a 1 line change, then save and the auto formatter changes another 150 lines!

If we had a preset code-style formatter this can be avoided.

My personal preference is YAPF, which is similar to C++'s clang-format in that it doesn't care about any previous formatting and reformats to the rules that are chosen. This is different from other formatters (e.g. PyCharm's formatter will sometimes respect manual formatting of arguments, etc). Overall I don't care whether or not we chose YAPF as long as we have one!

Reproducible?

[Yes/No]

How to test the issue is resolved

• Tool added to dependencies
• CI Job that enforces formatting and fails if formatting doesn't match