'Retrieve the content at a given URL, or return None if the source
is unreachable.'

def fetch_url(self, url):

    try:
        with warnings.catch_warnings():
            warnings.simplefilter('ignore')
            r = requests.get(url, verify=False, headers={'User-Agent': USER_AGENT})
    except requests.RequestException as exc:
        self._log.debug(u'lyrics    request    failed:    {0}', exc)
        return
    if (r.status_code == requests.codes.ok):
        return r.text
    else:
        self._log.debug(u'failed    to    fetch:    {0}    ({1})', url, r.status_code)
