"+" suffix in 3.9.0+ breaks pip

[Cédric Cabessa]

python3.9 in focal is versioned as 3.9.0+

According to pip this is considered as a "LegacyVersion", which break comparison

https://github.com/pypa/pip/blob/20.2.4/src/pip/_vendor/packaging/version.py#L48

Here is a snippet that show the "+" break comparison

```
>>> from pip._vendor.packaging.version import parse
>>> parse("3.9.0+")
<LegacyVersion('3.9.0+')>
>>> parse("3.9.0")
<Version('3.9.0')>
>>> parse("3.9.0+") >= parse("3.6.0")
False
>>> parse("3.9.0") >= parse("3.6.0")
True
>>>
```

Is it possible to mark this version as 3.9.0 ?
It seems the plus is introduced by a debian patch.

Thank you

[Gert van Dijk (gertvdijk)]

It seems this version string was introduced in a upstream Debian patch indeed, when it was based on a prerelease version of Python 3.9. The patch (git-updates.diff) was dropped later.

Introduced (erroneously):
https://salsa.debian.org/cpython-team/python3/-/commit/5334a0144db8e35afa8ae898d0dbd06afa426ccb

Removed:
https://salsa.debian.org/cpython-team/python3/-/commit/7952d9ce65aa51d6a23107ce1e30d0d92b1e15c7

Please backport the updated Debian-packaged Python 3.9 to Ubuntu.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.