The distutils commands 'build_scripts' and 'install_data' both may end
up installing .py files.  Such .py file should be able tobe run through
lib2to3 in the same way supported by build_py.

pywin32 has ended up with something like:

    class my_build_scripts(build_scripts):
        def copy_file(self, src, dest):
            dest, copied = build_scripts.copy_file(self, src, dest)
            # 2to3
            if not self.dry_run and copied:
                refactor_filenames([dest])
            return dest, copied

where 'refactor_filenames' is (basically) the lib2to3 block from
build_py moved to a utility function.