TST: flaky test on 3.7

[jreback]

This is occasionally failing the CI.

running this multiple times will cause it to fail:
pytest pandas//tests/groupby/test_categorical.py --pdb -v -k apply -s

not sure where the error is yet. xfailing for now.

[TomAugspurger]

👍 I'll look into it today.

[TomAugspurger]

Some brief notes:

It's seemingly related to some process-level state. With pytest-repeat, I run pytest pandas/tests/groupby/test_categorical.py::test_apply --pdb -v --count=10. I either get all failures, or all passes; never a mix.

[jreback]

yeah something is weird. not really sure.