CLN: unify unicode file handle processing

[jreback]

xref #13351 (comment)

We use io/common/_get_handle and io/common/get_filepath_or_buffer in various places in most of the io modules, need to unify encoding handling to a somewhat simpler interface (1 function).

[max-sixty]

If this is backported from python 3.6, could it help? https://www.python.org/dev/peps/pep-0519/

[jreback]

we already support pathlib and py.path in an ok way _stringify_path. This is more about providing a uniform interface that just works with encoding (and compression, though we are almost there for that). It is not far away, just needs some refactoring.

[jreback]

@aterrel want to submit more this so can proceed on #13351 ?

[aterrel]

Yeah I can look into it more. I worked around the issue in #13351, so I feel it could go in before this issue is fixed.

[mroeschke]

I think #15008 encompasses this specific point. Close to close as a duplicate