A generator yielding the full path to the replays under `replay_dir`.

def replay_paths(self, replay_dir):
    """A generator yielding the full path to the replays under `replay_dir`."""
    replay_dir = self.abs_replay_path(replay_dir)
    if replay_dir.lower().endswith(".sc2replay"):
      yield replay_dir
      return
    for f in gfile.ListDir(replay_dir):
      if f.lower().endswith(".sc2replay"):
        yield os.path.join(replay_dir, f)