'Fail unless an exception of class excClass is thrown
by callableObj when invoked with arguments args and keyword
arguments kwargs. If a different type of exception is
thrown, it will not be caught, and the test case will be
deemed to have suffered an error, exactly as for an
unexpected exception.
If called with callableObj omitted or None, will return a
context object used like this::
with self.assertRaises(SomeException):
do_something()
The context manager keeps a reference to the exception as
the \'exception\' attribute. This allows you to inspect the
exception after the assertion::
with self.assertRaises(SomeException) as cm:
do_something()
the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)'

def assertRaises(self, excClass, callableObj=None, *args, **kwargs):

    context = _AssertRaisesContext(excClass, self)
    if (callableObj is None):
        return context
    else:
        with context:
            callableObj(*args, **kwargs)
        return
