raisesgroup followups

[jakkdl]

Followup to #13192, which got increasingly unwieldy towards the end so I'm going to do a couple followup PR's to clean up loose ends

• renames src/_pytest/raises_group.py to src/_pytest/raises.py
• moves pytest.raises from src/_pytest/python_api.py to src/_pytest/raises.py
• adds several newsfragments that should've been bundlen with add RaisesGroup & Matcher #13192
• add more detailed error message if you try to do RaisesGroup((ValueError, TypeError))
• spend way too much mental energy debating with myself if passing the wrong type to a function expecting an exception type is a TypeError or a ValueError, or if it matters at all

[Zac-HD]

looks good, but needs some merge fixes - consider rebasing?

[Zac-HD]

I think we really need to spell out this api, for people who aren't really familiar with Pytest. Something like

You can now pass :func:with pytest.raises(check=fn): <pytest.raises>, where fn is a function which takes a raised exception and returns a boolean. The test fails if no exception was raised (as usual with :func:pytest.raises), passes if an exception is raised and fn returns True, and re-raises the exception if fn returns False (which also fails the test).

[bluetech]

Hi, I missed the previous episode of this so I hope you don't mind me asking a question late.

1. I don't see documentation for the new check parameter in the pytest.raises docstring. Unless I missed it, can it be added?

2. Would you mind briefly recounting to me the rationale for check? (Feel free to tell me to just go read the previous discussion...). Do I intuit correctly that it is not really meant to be used with the expected_exception overload, but with the 2nd overload when more elaborate logic is needed than just an isinstance?