Invalid ref WARN msg

[rimutaka]

I see multiple Invalid ref msgs, but can't remember what they mean and if this can be a sign of a bigger problem.

E.g.

Apr 11 07:59:12.744  INFO pu{idx=0}: stackmuncher::tech: Removing local import: pip._internal.exceptions / Trial Code/lib/python3.8/site-packages/pip/_internal/exceptions.py
Apr 11 07:59:12.744  INFO pu{idx=0}: stackmuncher::tech: Removing local import: pip._internal.utils.typing / Trial Code/lib/python3.8/site-packages/pip/_internal/utils/typing.py
Apr 11 07:59:12.745  INFO pu{idx=0}: stackmuncher::tech: Removing local import: pip._internal.utils.logging / Trial Code/lib/python3.8/site-packages/pip/_internal/utils/logging.py
Apr 11 07:59:12.745  INFO pu{idx=0}: stackmuncher::tech: Removing local import: typing / Trial Code/lib/python3.8/site-packages/pip/_internal/utils/typing.py
Apr 11 07:59:12.745  INFO pu{idx=0}: stackmuncher::tech: Removing local import: pip._internal.utils.subprocess / Trial Code/lib/python3.8/site-packages/pip/_internal/utils/subprocess.py
Apr 11 07:59:12.746  INFO pu{idx=0}: stackmuncher::tech: Removing local import: pip._internal.vcs.versioncontrol / Trial Code/lib/python3.8/site-packages/pip/_internal/vcs/versioncontrol.py
Apr 11 07:59:12.747  INFO pu{idx=0}: stackmuncher::tech: Removing local import: pip._internal.utils.misc / Trial Code/lib/python3.8/site-packages/pip/_internal/utils/misc.py
Apr 11 07:59:12.747  INFO pu{idx=0}: stackmuncher::tech: Removing local import: logging / Trial Code/lib/python3.8/site-packages/pip/_internal/utils/logging.py
Apr 11 07:59:12.754  WARN pu{idx=0}: stackmuncher::kwc: Invalid ref:  _inputstream
Apr 11 07:59:12.755  WARN pu{idx=0}: stackmuncher::kwc: Invalid ref:  _tokenizer
Apr 11 07:59:12.755  WARN pu{idx=0}: stackmuncher::kwc: Invalid ref:  treebuilders
Apr 11 07:59:12.755  WARN pu{idx=0}: stackmuncher::kwc: Invalid ref:  _utils