Import mock from unittest.

[clokep]

These tests fail for me locally with builtins.ModuleNotFoundError: No module named 'mock'

I'm not sure why they're working in CI since we shouldn't be install mock anymore.

This also adds a license header. Broken from #11306.

[clokep]

I think this is having some issues with async mocks. I don't understand how the original code remotely worked without mock installed though?

[erikjohnston]

I think this is having some issues with async mocks. I don't understand how the original code remotely worked without mock installed though?

We added mock back in in #11306 as mock backports support for AsyncMock?

[clokep]

I think this is having some issues with async mocks. I don't understand how the original code remotely worked without mock installed though?

We added mock back in in #11306 as mock backports support for AsyncMock?

That's really confusing -- we put a bunch of work into removing this dependency. 😢

Anyway, it would be great to shout that dependencies updated!

[erikjohnston]

Ah, sorry I didn't realise we'd done that 🙁 TBH it was mostly me raging at the amount of faff to work around lack of async utils in py3.6

[clokep]

For cross referencing -- see #9772.

[clokep]

Oh hmm, I guess we should still grab the license header here. I'll do a separate PR.