Committed (with enhanced tests and a few fixes) in r85818

And credit where it's due to test___all__ for picking up a typo in my adjustment to tempfile.__all__ :)

I created issue #10188 to track the shutdown problem. I'm considering taking out the code that attempts to allow the __del__ method to work at shutdown though, since it isn't actually achieving anything (I wanted a record of it in the main repository, which is why I kept it for the initial checkin).