CI: Check for inconsistent pandas namespace usage
Adding a CI check that we aren't (for instance) using Series(...) and pd.Series(...) in the same file. ~This is kept intentionally small in scope (checking only DataFrame and Series for one file name right now) since this is very common in the code base and I'm not sure if this is something we'd actually want to enforce.~
I agree with @jreback: small preference towards not `pd.`, preference for within-file consistency, not worth bikeshedding on this topic yeah it think this is ok to add. will have to figure out the best way to expand this coverage. maybe a file for includes with the test files to check? (or a config like file). > yeah it think this is ok to add. will have to figure out the best way to expand this coverage. maybe a file for includes with the test files to check? (or a config like file).

The diffs will be very large but it may be easier just to fix this globally for the different classes. I did this for Series just now (can revert if the PR is too large) and could do for DataFrame, etc. if worthwhile. > > yeah it think this is ok to add. will have to figure out the best way to expand this coverage. maybe a file for includes with the test files to check? (or a config like file).
> 
> The diffs will be very large but it may be easier just to fix this globally for the different classes. I did this for Series just now (can revert if the PR is too large) and could do for DataFrame, etc. if worthwhile.

oh i think this is fine (yeah do DataFrame separately); only issue is have to make sure all passing (in case we are missing imports). ci is a bit cranky now. and actually merge master once again (as just merged big PR). ping when you are ready. > and actually merge master once again (as just merged big PR). ping when you are ready.

Looks to be mostly green (only annoying thing that can happen are false positives due to Series(...) being used in comments but not code, so I changed those as well) thanks @dsaxton 