message: checkoint dir test
diff: @@ -95,7 +95,8 @@ class DatabaseRunnerTests(unittest.TestCase):
  terminal_when=terminal_when,
  behaviors=behaviors_tested,
  log_eval_avg_every=1,
  - checkpoint_dir="checkpoints1/")
  + checkpoint_dir="checkpoints1/",
  + merge_existing=True)
  result = benchmark_runner2.run(checkpoint_every = 10)
  df = result.get_data_frame()
  @@ -188,7 +189,8 @@ class DatabaseRunnerTests(unittest.TestCase):
  behaviors=behaviors_tested,
  log_eval_avg_every=1,
  num_cpus=4,
  - checkpoint_dir="checkpoints2/")
  + checkpoint_dir="checkpoints2/",
  + merge_existing=True)
  # one run after 30 steps benchmark dumped
  result = benchmark_runner.run(checkpoint_every = 3)
  