Dec cleanup
- [X] closes #18190 
- [X] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

This should be the last commit to close out the issue referenced above. I think there's further opportunity to convert some of the imperative ``pytest.skip`` calls over to the new decorator methodology (especially Ibn ``pandas/tests/io``) but to keep the scope clean I would rather open a new issue for those rather than continually update #18190
Looking into Travis failures. I was only grepping the pandas directory for ``skip_if_no`` uses but looks like I missed some in ``conftest.py`` thanks @WillAyd very nice set of patches! @WillAyd General comment, please give your PRs a bit more descriptive title (@jreback please also do that before merging so the commit title is more informative when looking at the log)