Begin incorporating Python unit tests into build

We now build a separate APE binary for each test so they can run in
parallel. We've got 148 tests running fast and stable so far.

third_party/python/Lib/test/test_tempfile.py

@@ -13,6 +13,7 @@ from unittest import mock
 
 import unittest
 from test import support
+from encodings import utf_16
 from test.support import script_helper