Comment 2 for bug 882656

Ikpeer: you can try installing an earlier version of gradebook. Get it from
http://packages.ubuntu.com/natty/python-schooltool.gradebook

and install with

$ sudo dpkg --install python-schooltool.gradebook_0.9.0-0ubuntu1_all.deb

SchoolTool should now start without this error.

Then, you can upgrade gradebook again to the version from oneiric. Maybe this time evolution will succeed.