Re: Updated PEP 394 (python and python2 commands)

[Matthias Klose <doko@debian.org>]

On 19.05.2018 07:24, Stuart Prescott wrote:
> Matthias Klose wrote:
> > The distro should get
> > out of the way of using the python symlink, and giving users the freedom /
> > choice what to do about the link.
>
> I think I understand your rationale to stop shipping /usr/bin/python and
> once the unversioned symlink disappears from use in Debian then at least
> that particular avenue to breaking one's system disappears.
>
> What I don't understand is why any changes to package names or dependencies
> are required to achieve that goal.
>
> It sounds like a reasonable amount of work in your proposal, but once we no
> longer have any Python 2 applications left at some stage in the bullseye
> cycle, isn't the following sufficient?
>
> --- a/debian/rules
> +++ b/debian/rules
> @@ -247,12 +247,9 @@ binary-arch: build install stamp-doc
>   
>          : # provide the python and python.1 defaults
>          mkdir -p debian/python-minimal/usr/bin
> -       ln -sf python$(VER) debian/python-minimal/usr/bin/python
>          ln -sf python$(VER) debian/python-minimal/usr/bin/python2
>          mkdir -p debian/python-minimal/usr/share/man/man1
> -       ln -sf python$(VER).1.gz \
> -               debian/python-minimal/usr/share/man/man1/python.1.gz
>          ln -sf python$(VER).1.gz \
>                  debian/python-minimal/usr/share/man/man1/python2.1.gz
>
> and then either later in the bullseye or bookworm cycles, those python-
> defaults simply go away along with all the other 'unversioned' python module
> and interpreter packages.
>
> What have I (and others!) missed that would make a rather elaborate
> packaging dance preferable to this?

from my point of view this doesn't address:

 - being able to de-install the python command for buster, if
   people don't use it.  Most dependencies are auto-generated, so
   these could be replaced by dependencies on python2. I would
   assume that the majority of users won't have to install the
   python package anymore, unless they are doing python2
   development.

 - Not having a python package in bullseye (buster+1), but a
   python2 package doesn't point to any "default" anymore. Many
   users are installing just python, because it's the unversioned
   package.  So make it clear that this is another version, and
   with having the choice of python2 and python3, most users will
   install python3.

Note that with the command-not-found package installed (and using python3), and 
not having python installed, you get now a message

   $ python

   Command 'python' not found, but can be installed with:

   sudo apt install python3
   sudo apt install python

   You also have python3 installed, you can run 'python3' instead.

Assuming that you only have python2 installed in buster, you get this hint 
already in buster, pointing to python3. You can't do this without a separate 
python2 package.

Matthias