Returns a tf.train.CheckpointSaverHook for autosaving checkpoints.

def _configure_saver(checkpoint_dir, checkpoint_interval):
  """Returns a tf.train.CheckpointSaverHook for autosaving checkpoints."""
  saver = tf.train.Saver()
  return tf.train.CheckpointSaverHook(
      checkpoint_dir=checkpoint_dir,
      save_steps=checkpoint_interval,
      saver=saver)