f string in io.common
- [ ] ref #29547
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Thanks for the PR! Please run black on your changes - see the code_check github actions
```
Checking black formatting
would reformat /home/runner/work/pandas/pandas/pandas/io/common.py
Oh no! 💥 💔 💥
1 file would be reformatted, 875 files would be left unchanged.
``` If you merge master as @WillAyd suggested above test failures should be fixed  I think CI failure is unrelated yet again - can you merge master one more time to be sure? Hi,
I've attempted to merge to master, however, receive the following error messages. Any help much appreciated!

![errormsg](https://user-images.githubusercontent.com/21073989/70384297-94dfac80-1931-11ea-8f2d-313156fea5d0.JPG)
 @daniellebrown you need to ``git push origin shiny-new-feature -f`` @daniellebrown might want to try one more of:

```
git fetch upstream
git merge upstream/master
git push origin shiny-new-feature
```

To resolve CI failures @daniellebrown https://github.com/pandas-dev/pandas/pull/30022#issuecomment-561434493 see https://dev.pandas.io/docs/development/contributing.html#python-pep8-black Any advice on how to fix this error: 

would reformat /home/runner/work/pandas/pandas/pandas/io/common.py
Oh no! 💥 💔 💥
1 file would be reformatted, 880 files would be left unchanged.

I've run black several times and it doesn't seem to do the trick.  thanks @daniellebrown  very nice thanks @jreback @WillAyd @simonjayhawkins !