The following code in a unittest test is a no-op:

self.assertRaises(lambda: 1)

I would expect this to fail the test, because I naively assumed omitting the exception class would act as:

self.assertRaises(BaseException, lambda: 1)

verifying that *any* Exception is raised.



I believe the correct behaviour is to raise a TypeError if excClass is not a BaseException-derived type, similar to if a non-type is passed as the first arg to issubclass.

Attached is a patch to do so.  It also removes a no-op self.assertRaises from libimport's tests (because it started failing when I ran the tests with the patch).  That assertion is redundant, because the two lines above perform the assertion being attempted.