Hi,
I've seen this before and I'm fairly sure that it's an issue from the
system version of pip interacting badly with a pip-installed version
of pip. However, I also cannot reproduce it now.
It has been discussed upstream [1] and a compatibility layer has been
added to avoid it [2][3]. That may explain why it is seemingly
unreproducible now.
Instead of the error, I'm now receiving this when running a newer
pip-installed version through the system-installed version:
WARNING: pip is being invoked by an old script wrapper. This will
fail in a future version of pip.
Please see https://github.com/pypa/pip/issues/5599 for advice on
fixing the underlying issue.
To avoid this problem you can invoke Python with '-m pip' instead
of running pip directly.
All in all, I think the error in this bug is likely not caused by the
packaged version itself. The wrapper should probably be changed at
some point, though.
[1] https://github.com/pypa/pip/issues/5599
[2] https://github.com/pypa/pip/issues/7498
[3] https://github.com/pypa/pip/commit/3f4bb75
Regards,
Robin
