Treat some warnings as errors in CI

[tim-schilling]

Description

Explicitly ignores the RedirectPanel's deprecation warning.

Checklist:

• I have added the relevant tests for this change.
• I have added an item to the Pending section of docs/changes.rst.

[github-actions]

Coverage report

This PR does not seem to contain any modification to coverable code.

[matthiask]

I have to admit I'm confused. -W error would make warnings errors. -W always just makes us show warnings each time they are encountered, not just once per call location.

The tox.ini change makes us not show warnings all the time anymore, and additionally also ignores the redirects panel warning... I think that's fine, since using a warnings eating context manager is hard here.

However, the changelog entry doesn't seem to match what we're doing here?

[tim-schilling]

I forgot to update the changelog after I switched away from error. I'm going to change this though to follow what Adam does with django-mysql then ignore our specific warning.

      -W error::ResourceWarning \
      -W error::DeprecationWarning \
      -W error::PendingDeprecationWarning \

[matthiask]

Makes sense! Obviously we still have some problems to fix or to ignore if we want to merge this.