'An user cannot be activated anymore once the activation key is
already used.'

def test_activation_used_account(self):

    user = UserenaSignup.objects.create_user(**self.user_info)
    activated_user = UserenaSignup.objects.activate_user(user.userena_signup.activation_key)
    self.assertTrue(activated_user.userena_signup.activation_key_expired())
