Not sure why the pyodide test is failing.

I'm fine with xdoctest FWIW, testing dependencies are low cost.

I haven't added xdoctest integration to a project where nox was the driver. I think what I did is idomatic, but let me know if there is a way that makes more sense for cibuildwheel. I've added a similar invocation for doctests to the bin/run_tests.py script.

There are two things that need to happen to get doctests running with xdoctest:

1. pytest needs to be pointed at the source path, or the path to the installed package so it can parse the doctests.
2. the --xdoctest argument needs to be passed so the default doctest plugin is disabled and replaced with xdoctest.

Looking at the noxfile it looked like the unit test and bigger tests were separated, so I added a third call for doctests only, which points at cibuildwheel, assuming that the pytest command is running in the root of the repo. This should work because it seems the tests are run against an editable mode install.

I also added --xdoctest to the pytest section in pyproject. This means that all pytest calls will pick up any doctests in whatever directory they are run on. The other option is pass it to pytest directly in the nox file. Both options have advantages / disadvantages.

Looks like circleci has a "-k" filter that disables all doctests, and if pytest collects no tests, then it returns an exitcode of 5. So, I've added a special case to allow for that to happen. The alternative is that we could add "or cibuildwheel" to PYTEST_ADDOPTS, which will hit all doctests, but it also hits 3 other tests in unit_test that I think are enabled anyway. It's unfortunate that using "-k doctest" or "-k xdoctest" doesn't work. I may look into fixing that in a new xdoctest version.

Other changes:

• I had to add a special case to the doctest in OCIContainer as it hard codes image = _get_pinned_container_images()['x86_64']['manylinux2014']. It would have been nice if _get_pinned_container_images()[oci_platform.name] worked, but the pinned images want "x86_64" as the key and not "linux/amd64". I think it would be a little cleaner if there was a way to lookup corresponding pinned images for a platform enum, but I didn't want to add that complexity without running it by maintainers. So there is an extra skip case for now. I can make a concise helper for this to clean up the doctest if desired.

• I also too @joerick's suggestion to refactor the oci container unit tests with the native classmethod.

• Added "--ignore-glob=*venv*" to pytest to prevent pytest from collecting doctests in the virtual environment folders.