Hi everyone,

> python 3 does not ship a python binary any more, just a binary called
> python3. That could be useful, since it would allow to install python
> 2 and 3 side by side. However, all packages relying on a shebang
> substitution with a python binary now fail.

Here's what it looks like on my Parabola system, which I think is a sane
way of doing it (ok, there's no *truly* sane way of doing it):

$ ls -l /usr/bin/python*
lrwxrwxrwx 1 root root  1K May 21 17:50 /usr/bin/python -> python3
lrwxrwxrwx 1 root root  1K May 21 17:50 /usr/bin/python-config -> python3-config
lrwxrwxrwx 1 root root  1K May 12 18:01 /usr/bin/python2 -> python2.7
lrwxrwxrwx 1 root root  1K May 12 18:01 /usr/bin/python2-config -> python2.7-config
-rwxr-xr-x 1 root root  7K May 12 18:01 /usr/bin/python2.7
-rwxr-xr-x 1 root root  2K May 12 18:01 /usr/bin/python2.7-config
lrwxrwxrwx 1 root root  1K May 21 17:50 /usr/bin/python3 -> python3.3
lrwxrwxrwx 1 root root  1K May 21 17:50 /usr/bin/python3-config -> python3.3-config
-rwxr-xr-x 2 root root 11K May 21 17:50 /usr/bin/python3.3
lrwxrwxrwx 1 root root  1K May 21 17:50 /usr/bin/python3.3-config -> python3.3m-config
-rwxr-xr-x 2 root root 11K May 21 17:50 /usr/bin/python3.3m
-rwxr-xr-x 1 root root  2K May 21 17:50 /usr/bin/python3.3m-config

$ ls -l /usr/bin/idle*
lrwxrwxrwx 1 root root 1K May 21 17:50 /usr/bin/idle -> idle3
-rwxr-xr-x 1 root root 1K May 12 18:01 /usr/bin/idle2
lrwxrwxrwx 1 root root 1K May 21 17:50 /usr/bin/idle3 -> idle3.3
-rwxr-xr-x 1 root root 1K May 21 17:50 /usr/bin/idle3.3

$ ls -l /usr/bin/pydoc*
lrwxrwxrwx 1 root root 1K May 21 17:50 /usr/bin/pydoc -> pydoc3
-rwxr-xr-x 1 root root 1K May 12 18:01 /usr/bin/pydoc2
lrwxrwxrwx 1 root root 1K May 21 17:50 /usr/bin/pydoc3 -> pydoc3.3
-rwxr-xr-x 1 root root 1K May 21 17:50 /usr/bin/pydoc3.3

$ ls -l /usr/bin/2to3*
lrwxrwxrwx 1 root root 1K May 21 17:50 /usr/bin/2to3 -> 2to3-3.3
-rwxr-xr-x 1 root root 1K May 12 18:01 /usr/bin/2to3-2.7
-rwxr-xr-x 1 root root 1K May 21 17:50 /usr/bin/2to3-3.3

I think Debian is similar, but with Python 2 being the default rather
than Python 3.

Shebangs are routinely changed in Parabola to accommodate this but since
shebangs are also routinely being changed in Guix anyway, this shouldn't
be a problem. 

So, the install scripts will require a bit of post-processing to
generate the symlinks and to move around some binaries to avoid
conflicts, but I think this is the only thing you can do.

Cheers, 
-brandon

ps - great meeting some of you last week in Paris!

-- 
Brandon Invergo
http://brandon.invergo.net