Comment 5 for bug 1087512

Yes, *please* backport this to 12.04.

By the way there was a workaround that allowed proxy authentication to work with https in the old version, but unfortunately this will break once the fix ships (not surprising, since it shamelessly abuses the overly permissive URI parser in apt):

Acquire::http::proxy "http://username:password@hostname:port";
Acquire::https::proxy "http://username:password@username:password@hostname:port";

(In other words, duplicating the username:password@ part for the https proxy only.)

Again, I recommend against using this, since your apt config will stop working once this fix is backported.