AttributeError: 'CourseWorksheet' object has no attribute 'getCategoryWeights' - adding worksheet to course

[alchemist]

Ubuntu 13.04 64bit
Schooltool 2.4.1

Adding worksheet to course

Server Error
An internal server error has occurred. This most likely means that you have found a bug in SchoolTool. Please report it on the issue tracker.

Exception
AttributeError: 'CourseWorksheet' object has no attribute 'getCategoryWeights'

Traceback
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.FlourishCourseWorksheetsView_deployed_worksheets.html object at 0x7fe2b473c3d0>
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 89, in __call__
  self.update()
File "/usr/lib/python2.7/dist-packages/schooltool/gradebook/browser/course_worksheets.py", line 348, in update
  self.deploy(self.course, term, template)
File "/usr/lib/python2.7/dist-packages/schooltool/gradebook/browser/course_worksheets.py", line 268, in deploy
  copyActivities(removeSecurityProxy(template), deployedWorksheet)
File "/usr/lib/python2.7/dist-packages/schooltool/gradebook/browser/report_card.py", line 86, in copyActivities
  for category, weight in sourceWorksheet.getCategoryWeights().items():