bzr-gtk version 0.100.0+bzr731-1 failed to build in oneiric

bzr-gtk version 0.100.0+bzr731-1 failed to build in oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2689755

Details about the rebuild:
http://people.ubuntuwire.org/~wgrant/rebuild-ftbfs-test/test-rebuild-20110816-oneiric.html

Direct link to the build log: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2689755/+files/buildlog_ubuntu-oneiric-i386.bzr-gtk_0.100.0%2Bbzr731-1_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 784 lines into the build log:

running build_scripts
creating build/scripts-2.7
copying and adjusting bzr-handle-patch -> build/scripts-2.7
copying and adjusting bzr-notify -> build/scripts-2.7
changing mode of build/scripts-2.7/bzr-handle-patch from 664 to 775
changing mode of build/scripts-2.7/bzr-notify from 664 to 775
   debian/rules override_dh_auto_test
make[1]: Entering directory `/build/buildd/bzr-gtk-0.100.0+bzr731'
BZR_PLUGINS_AT=gtk@/build/buildd/bzr-gtk-0.100.0+bzr731 xvfb-run -a /usr/bin/bzr selftest -s bp.gtk
bzr: ERROR: No module named gtk.gdk
You may need to install this Python library separately.
make[1]: *** [override_dh_auto_test] Error 3
make[1]: Leaving directory `/build/buildd/bzr-gtk-0.100.0+bzr731'
make: *** [build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110820-1814
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/bzr-gtk-0.100.0+bzr731