test for #17517 category name None after set_category() change
This test is for #17517 
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @Giftlin! Thanks for updating the PR.



Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on September 14, 2017 at 04:39 Hours UTC pls add to the original PR #17517  via another commit. separate PR's are for separate issues.