It is strange that 2.6 worked. Maybe you upgraded Ubuntu, too?
Try restarting schooltool
$ sudo service schooltool stop $ sudo service schooltool start
See https://answers.launchpad.net/schooltool/+question/254111
The bug is https://bugs.launchpad.net/ubuntu/+source/zope.html/+bug/1306986 but that has been fixed long ago.
It is strange that 2.6 worked. Maybe you upgraded Ubuntu, too?
Try restarting schooltool
$ sudo service schooltool stop
$ sudo service schooltool start
See https:/ /answers. launchpad. net/schooltool/ +question/ 254111
The bug is https:/ /bugs.launchpad .net/ubuntu/ +source/ zope.html/ +bug/1306986 but that has been fixed long ago.