'Returns the URL to use for downloading an episode\'s thumbnail. Uses
theTVDB.com data.
ep_obj: a TVEpisode object for which to grab the thumb URL'

def _get_episode_thumb_url(self, ep_obj):

    all_eps = ([ep_obj] + ep_obj.relatedEps)
    if (not helpers.validateShow(ep_obj.show)):
        return None
    for cur_ep in all_eps:
        myEp = helpers.validateShow(cur_ep.show, cur_ep.season, cur_ep.episode)
        if (not myEp):
            continue
        thumb_url = getattr(myEp, u'filename', None)
        if thumb_url:
            return thumb_url
    return None
