It seems that many people think you need distribute if you want to run 2to3 automatically in your setup.py. But personally I don't like setuptools (aka distribute) and hence don't like forcing this on users. No worries since plain old distutils supports this as well, but it simply appears less well known.

All you need to do is use the build_py_2to3 command supplied by distutils.command.build_py in python3 instead of the normal build_py command. This is how you can do this:

try:
    from distutils.command.build_py import build_py_2to3
except ImportError:
    pass

COMMANDS = {}
if sys.version_info[0] == 3:
    COMMANDS['build_py'] = build_py_2to3
setup(..., cmdclass=COMMANDS, ...)

That's it! Ok, you have to do slighty more then just add a keyword argument to the setup() call. But just the 2to3 feature is not worth using distribute for.