can't grade cando project

Hi.

If i try do grade a cando projekt, i get an error.

It is a shame that the function don't work. We would really like to use it..

this is the error report:

Tjenerfeil
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Unntak
AttributeError: 'NoneType' object has no attribute '__parent__'

Sporingsdata
File "/usr/lib/python2.7/dist-packages/zope/publisher/publish.py", line 132, in publish
  result = publication.callObject(request, obj)
File "/usr/lib/python2.7/dist-packages/zope/app/publication/zopepublication.py", line 205, in callObject
  return mapply(ob, request.getPositionalArguments(), request)
File "/usr/lib/python2.7/dist-packages/zope/publisher/publish.py", line 107, in mapply
  return debug_call(obj, args)
Extra information: <schooltool.skin.flourish.zcml_content.ProjectsGradebookOverview_index.html object at 0x7f91845e2310>
File "/usr/lib/python2.7/dist-packages/zope/publisher/publish.py", line 113, in debug_call
  return obj(*args)
File "/usr/lib/python2.7/dist-packages/schooltool/skin/flourish/page.py", line 98, in __call__
  self.update()
File "/usr/lib/python2.7/dist-packages/schooltool/gradebook/browser/gradebook.py", line 1167, in update
  GradebookOverview.update(self)
File "/usr/lib/python2.7/dist-packages/schooltool/gradebook/browser/gradebook.py", line 656, in update
  student['object'], activity, cell_score_value, evaluator)
File "/usr/lib/python2.7/dist-packages/schooltool/cando/gradebook.py", line 102, in evaluate
  equivalent = self.filterEquivalent(activity.findAllEquivalent())
File "/usr/lib/python2.7/dist-packages/schooltool/cando/gradebook.py", line 97, in filterEquivalent
  equivalent)
File "/usr/lib/python2.7/dist-packages/schooltool/cando/gradebook.py", line 96, in <lambda>
  lambda e: ISection(e.__parent__, None) is self.section,
File "/usr/lib/python2.7/dist-packages/zope/component/hooks.py", line 119, in adapter_hook
  return siteinfo.adapter_hook(interface, object, name, default)
File "/usr/lib/python2.7/dist-packages/schooltool/cando/gradebook.py", line 266, in getCourseSkillSetSection
  return worksheet.__parent__.__parent__

Modules
schooltool 2.8.5 (/usr/lib/python2.7/dist-packages)

schooltool.cando 2.8.2 (/usr/lib/python2.7/dist-packages)

schooltool.gradebook 2.8.4.1 (/usr/lib/python2.7/dist-packages)

schooltool.intervention 2.7.0 (/usr/lib/python2.7/dist-packages)

schooltool.lyceum.journal 2.8.2.1 (/usr/lib/python2.7/dist-packages)

Runtime
Python 2.7.6 (default, Jun 22 2015, 17:58:13) [GCC 4.8.2]

Linux schooltool 4.4.0-34-generic #53-Ubuntu SMP Wed Jul 27 16:06:39 UTC 2016 x86_64 x86_64

Filesystem encoding ANSI_X3.4-1968, preferred ANSI_X3.4-1968