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

[Karl Berry]

    I thought the intention was to prioritize python 3.X which
    would cause problems using "python" first.

Yes ... but I feel strongly that we should try very hard not to break
existing configure setups.

It occurs to me that we could allow maintainers to specify p3-searching
options in their configure.ac, like

AM_PYTHON_OPTS(python3-check-first python-check-omit)

(Or additional args to AM_PATH_PYTHON, whatever.)

That wouldn't have any compatibility issues, and would allow maintainers
to control what gets looked for, for packages that need to force python3.
(Other options could force looking for p2 first.)

Would that make sense? --thanks, karl.