Before attempting to follow this HOWTO, I asked around at #python about upgrading to Python 3.1.1 in Jaunty.
These things I only learned from there:
An important thing to note is that Jaunty uses Python 2.6 as a system default. According to their advice, this command could cause problems
sudo make install      # may cause problems
So instead of that, it should be
sudo make altinstall