Feature or enhancement

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

	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)

The returned value's type is not shown. It can be useful for users
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.