STY: Spaces over concat strings - batch 1
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I personally prefer the spaces at the start of the strings. I find it easier to spot missing spaces. not sure what others think. No strong preference but I think OK. @MomIsBestFriend can you merge master? Thanks @MomIsBestFriend 