fixup! fixup! Zope2: use func_code if __code__ is missing, that is the case for Script (Python).

nexedi/erp5@21f85a6f
added zope2 compatibility, but nexedi/erp5@21f85a6f (comment 180420) noted
the given assumption isn't true, which is why fixup commit nexedi/erp5@7a2c616e was
added. But nexedi/erp5@21f85a6f (comment 184548) noted
that nexedi/erp5@7a2c616e missed one case,
which is why this fixup commit is added. Now everything should be ok.