tie lint output into github annotations

[richvdh]

In github actions, it's possible to define some regexes which get matched against the script output, and allow individual lines in the PR to be annotated accordingly. It would be nice to do this for our linters.

See https://github.com/actions/toolkit/blob/master/docs/problem-matchers.md, and https://github.com/TrueBrain/actions-flake8/blob/main/action/flake8-matcher.json for an example

[callahad]

Would be very nice to have, but not sure we're going to be able to formally prioritize. For an example, dig into https://github.com/twisted/twisted/

[richvdh]

see https://github.com/twisted/twisted/pull/1631/files#diff-0aee9d699c9dba9eb4f2ea2d21a1ab0b4b3d90eda2fa31a31a02c143b975a101R670 for example of annotations on PR branches. (Of course, that annotation may have been fixed by the time you read this)

[richvdh]

ah, in that case it might be codecov.io which adds the annotation, rather than GHA itself.