message: Fix flaky saver_test. Don't trust sleep to sleep through the night.
diff: @@ -1261,8 +1261,12 @@ class KeepCheckpointEveryNHoursTest(test.TestCase):
  }, max_to_keep=2, keep_checkpoint_every_n_hours=0.7 / 3600)
  self.assertEqual([], save.last_checkpoints)
  - # Wait till 0.7 second have elapsed so s1 will be old enough to keep.
  - time.sleep((time.time() + 0.7) - start_time)
  + # Wait till 1 seconds have elapsed so s1 will be old enough to keep.
  + # sleep may return early, don't trust it.
  + now = time.time()
  + while now - start_time <= 1:
  + time.sleep(1)
  + now = time.time()
  s1 = save.save(sess, os.path.join(save_dir, "s1"))
  self.assertEqual([s1], save.last_checkpoints)
  