Add typing with PyAnnotate to ./tests

[DanielNoord]

• Add yourself to CONTRIBUTORS if you are a new contributor.
• Add a ChangeLog entry describing what your PR does.
• If it's a new feature, or an important bug fix, add a What's New entry in
  doc/whatsnew/<current release.rst>.
• Write a good description on what the PR does.

	Type
✓	🔨 Refactoring

Description

I thought I would try and see if I could use pyannote to do some typing for ./pytest.

I have split the changes into commits for each directory, sorry for the size of the PR I think this is about the limit of easy reviewing.

[coveralls]

Pull Request Test Coverage Report for Build 1197891429

• 5 of 5 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.0005%) to 93.098%

---

Totals
Change from base Build 1197864226:	-0.0005%
Covered Lines:	13232
Relevant Lines:	14213

---

💛 - Coveralls

[DanielNoord]

For some reason mypy_extensions is not available on the windows test suite? Is this a known issue?

[Pierre-Sassoulas]

This looks really good, thank you. There's only this issue with the match change that needs to be addressed.

[DanielNoord]

I think this is now good to go!

[Pierre-Sassoulas]

Thank you, this is going to help tremendously for putting mypy in place. And it's giving me idea for astroid :)

[DanielNoord]

If I can find the time I would be willing to start this up for astroid as well. Although I would first finish doing all of PyAnnotate for the pylint codebase!

[Pierre-Sassoulas]

If I can find the time I would be willing to start this up for astroid as well. Although I would first finish doing all of PyAnnotate for the pylint codebase!

I started something for astroid, pylint-dev/astroid#1163, but there will be a lot of work before being able to add mypy. pyannotate had some bug I had to manually fix the configuration json. We could discuss this in detail on the astroid's MR.

[DanielNoord]

Going to look at pylint-dev/astroid#1163 tomorrow.

Is there anything needed for this PR to be merged?