[bug#71672] [PATCH] python: Prefer python3 over python

Zack Weinberg wrote:
> Automake's python.m4 should also define these if they are not already defined.
> Then, we split AM_PATH_PYTHON into the part that sets PYTHON, which is implemented
> in terms of the above macros (but still looks for both 2 and 3) and the part that
> does all the rest of it.  People who want a slightly more efficient v3-only configure
> script can use AC_PATH_PYTHON3 + whatever the name of the new "all the rest of it"
> macro is.
> 
> I think that should disentangle things reasonably well, but we should definitely
> do this early rather than late in an automake release cycle, and seek out feedback
> from existing users of AM_PATH_PYTHON.  What say you?

I like this idea and am happy to help after the upcoming release.

Maybe something like:

    AM_PYTHON_SETUP([PYTHON-EXECUTABLE])

Which does all the extra $(pyexecdir), $(pkgpyexecdir), etc. given the
python executable. It should be pretty simple to move all the code
from AM_PATH_PYTHON to that separate macro since it should run on all
supported versions of Python (2 and 3).

Collin