So, vendored typing_extensions of pip seems to use the attribute. Maybe we should fix pip and typing_extensions first with a version guard?

I submitted a change to typing-extensions to stop unconditionally re-exporting this name. We should probably not merge this until that change to typing-extensions has been released.

fwiw this prevents usage of pip with the latest nightly -- perhaps this should be reverted until a pip release occurs?

(for example: this prevents promotion of deadsnakes nightly 3.15 because we check that pip, venv, and virtualenv are functioning): https://github.com/deadsnakes/py3.15/actions/runs/18678417262/job/53253774210

pip plans to release on Friday (24th): pypa/pip#13522 (comment)

A