TST: Update for pytest 7

[StefRe]

Remove 36 PytestRemovedIn8Warning and PytestReturnNotNoneWarning warnings.

[StefRe]

Python 3.5 and 3.6 are no longer supported by ubuntu-latest (22.04) on Github workflows.

[phobson]

@StefRe thanks for the update! I can take a look at this soon

[phobson]

@StefRe -- anything else you think should go in here?

[StefRe]

Looking at the CI test output, there are still 16 warnings. I think they are all due to missing pytest plugins:

• PytestConfigWarning: Unknown config option: pep8ignore
  --> maybe we can remove this from setup as the tests files are checked with black anyway, so there shouldn't be any PEP8 violations in there
• PytestReturnNotNoneWarning for all tests decorated with mpl_image_compare. I guess this is because the pytest-mpl plugin is not properly installed. I don't see these warnings locally with pytest-mpl version 0.16.1 installed. If I'm not mistaken it turns out that CI doesn't test anything for all these tests and this went unnoticed with pytest versions < 7.

[StefRe]

I only now saw that all the tests are run twice: first in Basic unit tests and then in Image comparison tests. The latter installs pytest-mpl and hence runs without warnings. Both workflows run, however, the complete test suite. What is actually the idea behind splitting the tests into two workflows?

[phobson]

What is actually the idea behind splitting the tests into two workflows?

I'm sure I had a reason at the time. Maybe the img tests were flaky and allowed to fail? In any case, I can't think of a good reason now.

[phobson]

Oh also the img tests are only run on the "latest" version of python, not e.g., 3.8, 3.9, etc. Maybe that should change

[StefRe]

My point was that Basic unit tests and Image comparison tests do the same thing, i.e. all tests are run twice (even more so now that the python version matrices are identical). So if we want to run the image comparison tests separately then maybe it's clearer to add -m "not mpl_image_compare" to python check_probscale.py --doctest-modules in python-runtests-basic.yml and -m mpl_image_compare to python check_probscale.py --mpl --doctest-modules in python-runtests-img-comp.yml, respectively.

[phobson]

Yeah I agree. Since all python versions in the img-comp matrix are passing, I'd be inclined to scrap the "vanilla" tests altogether.