We should add some stdlib links to the relevant docs:

• If you want to get a list of warnings, but no error if no warnings were emitted, use warnings.catch_warnings()
• To say "any warning here is unexpected / an error", use with catch_warnings(): simplefilter("error"); ...

I didn't intend to break anything, but nor did I consider that people might be using pytest.warns() like warnings.catch_warnings(). My apologies for the inconvenience!

Originally posted by @Zac-HD in #8677 (comment)