Custom build variables (e.g. CXX_STD or CXX) read from
mapnik-settings.env have to be provided as command line arguments
because SCons does not respect the environment variables.
¬
Fall back on `python`. Unlike the solution in PR #2395 this¬
puts all the responsibility for selecting the right python in the¬
case that "python" is Python 3 on the user. I've followed the lead¬
of the Python documentation Makefile. See
http://hg.python.org/cpython/file/340d48347295/Doc/README.txthttp://hg.python.org/cpython/file/340d48347295/Doc/Makefile
Intent is that if your `python` is Python 2 everything works as
before and that is your `python` is Python 3 but you have a
`python2` you can specify that instead.¬
Conflicts:
run_tests
