Distributions upgrading to Python 3

[Patrick McCarty]

Hello,

Arch Linux will be migrating to Python 3 very soon, and I'm trying to
figure out what to do with regard to LilyPond's build system.  I don't
know if Arch Linux is the first distribution upgrading to Python 3,
but this migration will be happening any day now.

The distribution-wide policy is as follows: Any applications that
still need Python 2 will depend on the "python2" package, which
provides a "python2" symlink to the currently installed Python 2
executable (in this case, soon to be "python2.7").

I know that LilyPond proper is not going to migrate yet,
understandably, so I will soon need to use the "python2" package.

There are two issues I am running into:

--) Two scripts still have "/usr/bin/python" lines
(python/auxiliar/manuals_definitions.py, and scripts/build/pytt.py).
Those should be changed to "@PYTHON@", right?

--) Some scripts use "/usr/bin/env python", which IIRC, is the best
solution for Mac OS X users.  However, I would need "/usr/bin/env
python2" instead for these scripts to work.

The rest of the scripts use either "@PYTHON@" or "@TARGET_PYTHON@",
which are substituted early in the make process.  This is just a
matter of detecting the appropriate Python at the configure stage.

Would it be feasible to use "#!/usr/bin/env @PYTHON@" or
"#!/usr/bin/env @TARGET_PYTHON@" for all Python scripts, using the
basename of the appropriate Python executable in place of the Make
variables?

Any thoughts about this?


Thanks,
Patrick