since it affects downstream users

The correct solution appears to be
https://rules-python.readthedocs.io/en/stable/toolchains.html#library-modules-with-dev-only-python-usage

This change also includes a workaround for the new mechanism creating
paths that are too long for Windows to handle.

Backport of 3e3b44c300b21eb996a2957782421bc0f157af18