Issue #16190: fix random module recommendation to use ssl.RAND_bytes().
Issue #1666318: Add a test that shutil.copytree() retains directory permissions.
Patch by Catherine Devlin.
#18707: point to Doc/README.txt in the README file.  Patch by Madison May.
Issue #18756: Improve error reporting in os.urandom() when the failure is due to something else than /dev/urandom not existing.
Issue #18743: Fix references to non-existant "StringIO" module.
Issue #16463: Fix a transient test_timeout failure.