Use `tmp_path` pytest fixture over `tmpdir`

[matthewfeickert]

tmp_path is a modern replacement for tmpdir, by the way.

Thanks and noted.

From the pytest docs (https://docs.pytest.org/en/7.1.x/how-to/tmp_path.html#the-tmpdir-and-tmpdir-factory-fixtures):

The tmpdir and tmpdir_factory fixtures are similar to tmp_path and tmp_path_factory, but use/return legacy py.path.local objects rather than standard pathlib.Path objects.

Note

These days, it is preferred to use tmp_path and tmp_path_factory.

In order to help modernize old code bases, one can run pytest with the legacypath plugin disabled:

pytest -p no:legacypath

This will trigger errors on tests using the legacy paths. It can also be permanently set as part of the addopts parameter in the config file.

We'll fix this up in another PR. 👍

Originally posted by @matthewfeickert in #2363 (comment) given feedback from @henryiii