Style: Use type.__name__ in raises error messages for consistency

[dariomesic]

Purpose

Addresses a FIXME in testing/python/raises_group.py that pointed out the inconsistent use of repr(type) vs type.__name__ in error messages.

This PR refactors the RaisesContext.__exit__ method in src/_pytest/raises.py to consistently use type.__name__ (e.g., 'ValueError') instead of repr(type) (e.g., <class 'ValueError'>) in all "DID NOT RAISE" error messages. This improves the readability and consistency of these assertion failures.

Tests

Because the library's error message format was changed, this PR also updates all the tests in testing/python/raises.py and testing/python/raises_group.py that were asserting the old, inconsistent message format.

[The-Compiler]

This makes me wonder if we should maybe use __qualname__ and possibly __module__ for non-builtins in the output, what do others think? IMHO it's fine without, as it should be clear from context.

[RonnyPfannschmidt]

i do wonder if this has the potentila to break plugin testsuites

[The-Compiler]

I think it's fair to do so. We've had it before that exception messages changed somehow, and often that required changes in pytest's testsuite and AFAIK sometimes elsewhere. Don't think exception messages are part of our API essentially.

[nicoddemus]

This makes me wonder if we should maybe use qualname and possibly module for non-builtins in the output, what do others think

Good question. It is an interesting idea, but I agree with you that it should be clear from context and has the potential of cluttering the output. I suggest we leave like this for now.

[jakkdl]

yeah as the comments mention I deliberately tried minimizing changes to behavior in pytest.raises when I added RaisesGroup.

[bluetech]

@nicoddemus @The-Compiler @jakkdl Since all of you approved the PR, I wonder if any of you want to push the green button?