message: Fix typo in CheckpointManager.
diff: @@ -577,7 +577,7 @@ class CheckpointManager(object):
  self._save_counter_assign = None
  if max_to_keep is not None and max_to_keep <= 0:
  raise ValueError(
  - ("Expected a positive integer or `None` for `max_to_max_to_keep`, "
  + ("Expected a positive integer or `None` for `max_to_keep`, "
  "got %d.")
  % (max_to_keep,))
  self._max_to_keep = max_to_keep
  