def METHOD_NAME(app, patron_martigny):
    """Test additional email for a patron."""
    Patron.validate(patron_martigny)
    user = patron_martigny.user
    original_user_email = user.email
    user.email = None
    patron_martigny['patron']['communication_channel'] = 'email'
    with pytest.raises(ValidationError) as e:
        Patron.validate(patron_martigny)
    assert 'At least one email should be defined for an email ' \
           'communication channel' in str(e)
    user.email = original_user_email