CI: test failure, raises unexpected warning

[phofl]

I merged master into #33247 . This results in a failing test:
pandas/tests/plotting/test_converter.py::TestRegistration::test_pandas_plots_register

in Windows py37_np_18

 AssertionError: Caused unexpected warning(s): [('DeprecationWarning', DeprecationWarning("Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3,and in 3.9 it will stop working")

Was this already detected?

test results

[TomAugspurger]

Will need a similar fix as https://github.com/pandas-dev/pandas/pull/34721/files#diff-fb957a9fbb8d57904092e2bbe06b1b2bR99-R109.

[jbrockmendel]

Has this been fixed?

[mroeschke]

Looks like we're not testing py37_np_18 anymore, and an analgous py37_np_18 build doesn't seem to have this warning anymore so I think we can close. Can open a new issue if this reappears.

https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=64034&view=logs&jobId=404760ec-14d3-5d48-e580-13034792878f&j=404760ec-14d3-5d48-e580-13034792878f&t=f81e4cc8-d61a-5fb8-36be-36768e5c561a