Prepare for Pytest v8

[ksunden]

PR summary

The behavior of pytest.warns has changed, particularly with regards to handling of additional warnings

When additional warnings that were not tested for are raised, I simply add a filterwarnings (some are artifacts of with blocks).

And there are a couple that seem are not actually currently warning at all, but had been occluded by a pytest.errors.

PR checklist

• "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

[dstansby]

Is any the CI for this PR running with pytest 8 to check that these fixes do indeed work? Or should I install pytest 8 locally to check?

[ksunden]

Looks like I need to figure out a way of fixing one particular test so that it works in both pytest 7 and 8...

I did indeed just install pip install -U --pre pytest to test locally. I think the scheduled prerelease ci run may catch it, but I don't think we have that set up to run on PR via a label like we do for some other CI runs.

[ksunden]

Yeah, that particular test raises 2 separate warnings on the same line of code, pytest 7 swallows the outer one and so you get "did not warn", pytest 8 passes it through, so if you don't have both it gets raised... I think I just need to filter the deprecation warning here as it is already tested earlier in the test.