Build fails with scons > 2.4.1

[noahp]

Modern scons appears to force from future __import__ print_function, so these sconscripts don't work past 2.4.1 (2.5.1 from pypi! or 3.0.0 latest scons).

scons futurized in 2016:
https://bitbucket.org/scons/scons/commits/996d359c35f5a7abf8b91b7095ff27d38780627c)

[barbibulle]

Thanks for the report. Will get fixed ASAP.