CLN: imports in pandas/io/excel/_base.py
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

lgtm - not sure on doc failure. Try merging master? Thanks @MomIsBestFriend 