Python 3 binaries

[Andreas Enge <andreas@enge.fr>]

Hello,

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.

I see two general possibilities to solve the problem:
- The simplest one, add a symlink python->python3 in the python 3 package.
  But then we lose the possibility of installing python 2 and 3 at the same
  time. Which maybe does not matter? It would only be a problem for a user
  wanting to install both in the user profile, while all other packages
  would internally have rewritten their calls to either of the two python
  versions
- In the patch-shebang phase, we could, if the python binary is not
  available, look for the python 3 binary. But that would mean special code
  only for python.

Personally, I would tend to the first solution. But what do you think?

Andreas