'If L{TestCase.assertIsInstance} is passed a custom message as its 3rd
argument, the message is included in the failure exception raised when
the assertion fails.'

def test_assertIsInstanceCustomMessage(self):

    exc = self.assertRaises(self.failureException, self.assertIsInstance, 3, str, 'Silly    assertion')
    self.assertIn('Silly    assertion', str(exc))
