[py3porters-devel] PEP 394 in debian? (/usr/bin/python could be python3)

[Daniel Kahn Gillmor]

On Fri 2018-02-23 00:52:23 -0500, Scott Kitterman wrote:
> As far as I know, /usr/bin/python will be retired the same time that python2.7 
> is removed from Debian.  Even after python2.7 is removed from Debian, there 
> will be users that build from source and use it for local scripts.  Pointing 
> /usr/bin/python at a python3 version will only cause gratuitous harm to our 
> users.  It is not going to happen while I'm one of the python/python3-defaults 
> maintainers.

I'm glad to hear that you are concerned about users with code of their
own that is not part of a debian package.  I share your concerns.

I'm not advocating for debian switching /usr/bin/python to point at
python3 at any time in the near future, don't worry.

> Given that, I don't see value added in swapping Depends python:any (<< 2.8), 
> python:any (>= 2.7.5-5~) with Depends: python2.7.  Can you explain why you 
> think this is better?  I don't see it.

It means that on well-configured systems, where i need to have some
python2-only debian packages installed, but where i'm also using some
non-packaged code whose upstream uses a /usr/bin/python shebang line to
mean "either 2 or 3" (as recommended by PEP 394), i can do the following
manually safely:

    apt purge python-minimal
    ln -s python3 /usr/bin/python

and then my external (non-packaged) code will be able to use python3
(which i might prefer over python2 for any number of reasons).

having packages convert their shebang lines while they adjust their
dependencies mean that apt will expose when it is safe (in terms of the
debian packaging) to do this change.  This would not be the case for
dpkg-divert, or other similar blunter solutions.

       --dkg
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