Add pylint missing-await checker

[belm0]

pylint support for #671

TODO:

• fix async generator false positive
• tests
• settle error name(s) and code numbers

This runs fine on trio codebase and my own codebase. I haven't looked hard for false negatives.

Run on trio codebase:

PYTHONPATH=. python3 -m pylint --load-plugins=trio.testing.pylint-missing-await --disable=all --enable=missing-await trio/

[codecov]

Codecov Report

Merging #700 into master will decrease coverage by 0.1%.
The diff coverage is 84.33%.

@@            Coverage Diff             @@
##           master     #700      +/-   ##
==========================================
- Coverage   99.52%   99.42%   -0.11%     
==========================================
  Files         102      105       +3     
  Lines       12192    12272      +80     
  Branches      904      916      +12     
==========================================
+ Hits        12134    12201      +67     
- Misses         36       48      +12     
- Partials       22       23       +1

Impacted Files	Coverage Δ
trio/_subprocess_platform/__init__.py	100% <100%> (ø)	⬆️
trio/tests/pylint-expect-message.py	100% <100%> (ø)
trio/_core/tests/test_run.py	100% <100%> (ø)	⬆️
trio/tests/test_pylint_missing_await.py	75% <75%> (ø)
trio/testing/pylint-missing-await.py	82.05% <82.05%> (ø)

[njsmith]

It looks like there's a convention of having standalone pylint-{projectname} projects, e.g.:

• https://github.com/PyCQA/pylint-celery
• https://github.com/PyCQA/pylint-django
• https://github.com/jschaf/pylint-flask

Maybe we should follow, with a pytest-trio (that would include this, and potentially other lints if we think of any)?

In other news, it looks like py38-dev and astroid have become incompatible, so our CI is currently broken... maybe we should just disable the static analysis tests when sys.version_info.releaselevel != "final"? This isn't the first time we've had trouble with this...

[belm0]

fixed false positive from async generators

[belm0]

• added tests
• missing-await run against trio code from check.sh

[Fuyukai]

This is like five years old and the project switched to ruff since. Closing.