assertRaises has callableObj listed as a keyword, though it is not possible to use it as a keyword when the callableObj takes arguments. 

The function definition is:
    def assertRaises(self, excClass, callableObj=None, *args, **kwargs):

Therefore, using it with a keyword such as:

    self.assertRaises(Exception, callableObj=my_function, args_to_function)

will fail due to passing arguments after a keyword.

Documentation [0] has callable listed as a positional argument, and this is how it should be used.

[0] https://docs.python.org/2.7/library/unittest.html#unittest.TestCase.assertRaises