This seems related to issue 10487. Some of the code is different in Python 3.  Since this is an enhancement, it seems unlikely to ever be accepted for 2.x, which is in bugfix-only mode.

Sadly, most hosting companies are still running Python 2.x, with many as old as 2.4.

Happily, you can patch your own copy to work; I did that, for both 2.x and 3.x, and described the issues in a set of bug issues, but haven't had the time to figure out how to go through the development process and submit individual patches: my code is kind of a bundled solution to all the issues I submitted, and it doesn't seem likely that a single patch to solve all the issues would be acceptable.  I'm happy to share my code, if it would help someone generate patches.