* Remove the chdir fixture.
* Re-enable fancy pytest asserts.
* Remove doc files from pytest ignores.
* Restore docs/_ext in test collection ignores.
* Skip a doctest that fails on Windows.
* Fix tests that were writing to the current dir.
* Switch to pytest.raises().
* Add matches= to broad pytest.raises().
* Adjust the test_nonserializable_object() regex for Python <= 3.11.
* Adjust the test_nonserializable_object() regex for PyPy.
* Adjust other test exception regexes for PyPy.
* Cleanup.