This function returns the list of configuration files to load.

    This is a callable so the configuration can be reloaded with files that
    changed in between.

def list_config_files() -> List[Text]:
    """
    This function returns the list of configuration files to load.

    This is a callable so the configuration can be reloaded with files that
    changed in between.
    """

    return [
        os.path.join(os.path.dirname(__file__), 'default_settings.py'),
        os.getenv(ENVIRONMENT_VARIABLE, ''),
    ]