def METHOD_NAME(self, mock_user_number_over_limit):
    mock_user_number_over_limit.return_value = False
    user_info = {
        # invalid email
        'email': USERNAME,
        'userid': randstring(40),
        'password1': 'password',
        'password2': 'password',
    }
    f = RegistrationForm(data = user_info)
    assert 'User %s already exists.' % USERNAME in str(f['email'].errors)