Код (ссылка на xml-ку рабочая):
xml_answer = urllib.urlopen('http://ws.audioscrobbler.com/2.0/?method=user.getlovedtracks&user=pOzit-tiV&api_key=b25b959554ed76058ac220b7b2e0a026&limit=50')
tree = etree.parse(xml_answer.read())
tree = etree.parse(xml_answer.read().decode('utf-8'))
tree = etree.parse(xml_answer.read().encode('utf-8'))