Improve deprecation warning message, when a test case returns non None value

[sobolevn]

Feature or enhancement

Right now there are two potential things we can improve in this warning message:

cpython/Lib/unittest/case.py

Lines 605 to 609 in 19435d2

	def _callTestMethod(self, method):
	if method() is not None:
	warnings.warn(f'It is deprecated to return a value that is not None from a '
	f'test case ({method})', DeprecationWarning, stacklevel=3)

1. The returned value's type is not shown. It can be useful for users
2. A common case for this warning is that async def test_some is defined in a regular TestCase class, I think that we can improve this specific case and suggest to use IsolatedAsyncioTestCase instead

I have a patch ready.

Linked PRs

• gh-120388: Improve deprecation warning message, when test returns non-None #120401

[AlexWaygood]

Thanks for doing this @sobolevn! :D