Some filter warnings in iptest seem to be ignored.

[Carreau]

Typically the ignore matplotlib UserWarning about rebuilding font cache. Who knows which other warnings filter could be ignored.

[Kojoley]

I did not replicate those warning filters for Pytest, so there should be no ignored warnings now, except the ones where the code explicitly hides it, and be aware that pytest.warns hides all warnings inside the with block: pytest-dev/pytest#9288.