def METHOD_NAME(self):
    """
    Method to ask source fetch the cover from its source into location at
    `self.cover_path`.
    If this method succeeds in putting the image from its source into
    `self.cover_path`, `fetch-success` signal shall be emitted and
    `fetch-failure` otherwise.
    Return value of this function doesn't have any meaning whatsoever.
    """
    self.fail('This source is incapable of fetching covers')