The attached patch updates lib2to3.tests and the test.test_lib2to3 script to use test discovery.  It also re-enables lib2to3.tests.test_all_fixers with a "cpu" resource guard.  That test has been failing since at least 3.2, but was never run anyway.  To allow it to pass, the patch adds "from __future__ import print_function" to lib2to3.main and lib2to3.tests.pytree_idempotency.