Comment 7 for bug 1281335

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

TypeError: sequence item 0: expected string, NoneType found

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 207, 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.MegaExporter_export.xls object at 0x7fadb90470d0>
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/export/export.py", line 757, in __call__
  self.export_section_timetables(wb)
File "/usr/lib/python2.7/dist-packages/schooltool/export/export.py", line 708, in export_section_timetables
  timetables.append(','.join(parts))

i need to know what happened to my school tool export
can i get some help