Trapped between unbundling policy and modified pkg_resources

[kitterma]

Environment

• pip version: 20.2
• Python version: Python3 3.8.2
• OS: Debian GNU/Linux Unstable

Description
There is a long standing issue when debundling regarding version comparisons failing. I think the best analysis of the problem is here: #5429 (comment). The result that even with the current pip with the current python3, errors still occur:

python3 -m pip list -o
ERROR: Exception:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/pip/_internal/cli/base_command.py", line 186, in _main
    status = self.run(options, args)
  File "/usr/lib/python3/dist-packages/pip/_internal/commands/list.py", line 158, in run
    packages = self.get_outdated(packages, options)
  File "/usr/lib/python3/dist-packages/pip/_internal/commands/list.py", line 165, in get_outdated
    return [
  File "/usr/lib/python3/dist-packages/pip/_internal/commands/list.py", line 167, in <listcomp>
    if dist.latest_version > dist.parsed_version
TypeError: '>' not supported between instances of 'Version' and 'Version'

I'm aware this has been, more than once, closed as a downstream issue, but I don't know what we're supposed to do about it. The pip _vendor README says "Note that partial debundling is NOT supported. You need to prepare wheels for all dependencies for successful debundling."

It seems to me that distros are stuck between a rock and a hard place on this. We have (for good reason and we appreciate pip's support for it) policies not to vendor packages. Pip's guidance is that if we are going to unvendor, then it needs to be everything, but problems like the above seem unavoidable.

Expected behavior
I understand that pip views this as a downstream issue. I'd like upstream advice (other than don't unvendor) on how we should address this.

How to Reproduce
On Debian Unstable (probably any Debian/Ubuntu, but I'm using 20.2 and Unstable for testing) install pip (sudo apt install python3 pip) and run the above command.

Thanks.

[kitterma]

This issue is better captured in pypa/setuptools#2052 - closing.