Comment 11 for bug 15093

Unfortunately, the prompt is governed by the PAM module. Most of them use a
variation of the expression you show, but if it shows something like:

Challenge 6789123hkjasd67:

That won't get it. What we need is a way to pass the prompt to gksudo (and to
gksu, I suppose) so it can be presented to the user correctly, and to have a
predictable prompt that these programs can look for to know when the auth token
needs to be entered.

We already allow certain % escapes with the sudo prompting mechanism. What may
be best is to add a new one for the PAM prompt string. You could then do
something like:

-p %p:GNOME_SUDO_PASS

and then strip out the ':GNOME_SUDO_PASS' and present the remainder to the user.
This means, however, some coordination between the two projects.