'Builds up the path to a banner thumb cache for a given Indexer ID
:param indexer_id: ID of the show to use in the file name
:return: a full path to the cached banner thumb file for the given Indexer ID'

def banner_thumb_path(self, indexer_id):

    bannerthumb_file_name = (str(indexer_id) + u'.banner.jpg')
    return ek(os.path.join, self._thumbnails_dir(), bannerthumb_file_name)
