def get_expected_validation_developer_message(preference_key, preference_value):
    """
    Returns the expected dict of validation messages for the specified key.
    """
    return "Value '{preference_value}' not valid for preference '{preference_key}': {error}".format(
        preference_key=preference_key,
        preference_value=preference_value,
        error={
            "key": ["Ensure this field has no more than 255 characters."]
        }
    )