message: This fixes an issue we are seeing with benchmarks.
diff: @@ -1458,7 +1458,7 @@ class Context(object):
  if policy is None:
  policy = MIRRORING_NONE
  - if self._mirroring_policy != policy:
  + if self._mirroring_policy is not None or self._mirroring_policy != policy:
  self._mirroring_policy = policy
  # Only set the policy if the context has already been initialized
  