def METHOD_NAME(self):
    """Ensure an error is raised when the difference isn't a
    valid support profile
    """
    def foo():
        strat_list = [self.support_profile[0], self.support_profile[4]]
        dif_profile = pygambit.StrategySupportProfile(
            strat_list, self.game
        )
        dif_profile - self.support_profile
    self.assertRaises(ValueError, foo)