Python2 and Python3 checks

[Matěj Týč]

Hello,

there is a Python autoconf support macro in automake AM_PATH_PYTHON that 
can be used to find Python interpreters.

The problem of this macro is that it treats Python versions in a linear 
manner - if I write that I want Python >= 2.7 on a machine that has 
Python 2.6 and Python 3.1, I probably want the rule to fail, not to 
assert that 3.1 >= 2.7, so it will pick this Python 3.1.

On a related note, a C library may build bindings for Python2 and for 
Python3, so in general, it seems to be a good idea to output results for 
more Python versions. Like to provide PYTHON2 and PYTHON3 instead of 
just PYTHON if the users desires so. My next observation is that in 
Makefile.am, one can use the foo_PYTHON to ensure special treatment of 
Python files during the installation s.a. compilation (and maybe 
something else?). I think that if I want to install bindings for Python2 
and Python3, each of them should be compiled with the interpreter of the 
corresponding major version.

The question stands like this: Is there a demand on automake side to fix 
this issue - to allow developers addressing multiple Python interpreters 
of different major versions? If so, I think that I can come up with some 
patches to get this working.

Best regards,
Matej Tyc