PSA: Debian Stretch, apt-listchanges, and Python 3

[Matt Ruffalo]

On 2016-08-29 23:56, Chris Angelico wrote:
> Up until very recently, the system Python has only been the Python 2.
> (For a while, it wasn't even 2.7, but I could easily use altinstall
> for that.) I have deliberately wanted to use 3.6 for ALL testing, not
> just by messing with venvs or shell aliases, in order to enforce
> dogfooding on everything (and for consistency); older Pythons are
> available as python3.4 and python3.5, but the live python3 has always
> been the one built from tip. And even as Debian starts to embrace Py3
> internally, this hasn't been a problem.
>
> If your goal is stability, sure. Don't mess with what 'env python3'
> runs. But if you want to thoroughly test stuff? That's different.
>
> ChrisA

This seems like a reasonably large problem on Debian's part. I was under
the impression that system-critical Python scripts used absolute paths
in their hashbang lines, to avoid exactly this situation. If something
really depends on the system Python version (whichever 2.x or 3.x that
might be), it should explicitly use that Python installation. User
scripts, of course, should use "/usr/bin/env python3" to be usable in a
virtualenv or under whatever Python installation the user chooses.

I believe the Gentoo package manager has logic to adjust the hashbang
lines of Python scripts if a package requests it, and I'm not as
familiar with Debian packaging but I'd be surprised if the Debian tools
were missing this functionality.

MMR...