This seems to be a bug in the autobuilder environment. python-gtk checks
if DISPLAY is set since the very first release. If it is not it does
not try to open the DISPLAY. Seems like somebody injected his DISPLAY
setting into the autobuilder environment and the DISPLAY is long gone
now...
I would try unsetting DISPLAY before running the configure script.
Also this bug should be reassigned to build.debian.org or whatever
the right package is.
Greetings
Torsten (python-gtk maintainer)