def prepare_config_uri(config_uri: str) -> str:
    """Make sure a configuration uri has the prefix ws://.

    :param config_uri: Configuration uri, i.e.: websauna/conf/development.ini
    :return: Configuration uri with the prefix ws://.
    """
    if not config_uri.startswith('ws://'):
        config_uri = 'ws://{uri}'.format(uri=config_uri)
    return config_uri