PR Summary

Pandas is planning to drop automatic registration of their converters for matplotlib so that import pandas no longer imports them. In preparation for that, we should deregister the pandas converters.

Note this should work fine for any of the tests. pandas converters were mainly for datetime, and I think our datetime converters now handle most of the cases properly.

Of course if we want to test pandas converters, separate tests could call pandas.plotting.register_matplotlib_converters().

#11391 (comment)

PR Checklist

• Has Pytest style unit tests
• Code is Flake 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way