def feed_url(itunes_lookup_response):
    """
    Returns feed URL from the itunes lookup response
    :param itunes_lookup_response:
    :return: str
    """
    if len(itunes_lookup_response.get('results')) == 0:
        raise LookupError("iTunes response has no results")
    url = itunes_lookup_response.get('results')[0].get('feedUrl')
    if url is None:
        raise LookupError("feedUrl field is not present in response")
    return url