def kafka_bootstrap_servers(request):
    """
    Return a comma-delimited string of Kafka bootstrap server host:port specified
    on the pytest command line with option --kafka-bootstrap-servers.

    Parameters
    ----------
    request : pytest request fixture

    Returns
    -------
    comma-delimited string of Kafka bootstrap server host:port
    """
    return request.config.getoption("--kafka-bootstrap-servers")