def parse_destinations_countries(conf):
    """Returns the destinations' country as string separated by comma.

    """
    destinations_countries = []
    for key in conf['destinations'].keys():
        # Not a destination key
        if key in ['usability_test_interval']:
            continue
        # The destination is not enabled
        if not conf['destinations'].getboolean(key):
            continue
        destination_section = 'destinations.{}'.format(key)
        destination_country = conf[destination_section].get('country', None)
        destinations_countries.append(destination_country)
    return ','.join(destinations_countries)