Al asignar un horario a un Sección

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Por favor, complete los pasos para reproducir el error aquí:
Varias secciones tienen horarios, pero cuando intenté en otra sección asignar un horio, generó un error.
Apagué y reinicié el servidor, pero el error continua.
Agradezco su ayuda.

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Exception

TypeError: ('Could not adapt', <schooltool.timetable.timetable.Timetable object at 0x7f8db42736e0>, <InterfaceClass schooltool.timetable.interfaces.IHaveTimetables>)

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.FlourishSelectedPeriodsAddTermsView_addTermsTimetable.html object at 0x7f8db4241650
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 96, in __call__
  self.update()
File "/usr/lib/python2.7/dist-packages/schooltool/skin/flourish/form.py", line 72, in update
  super(AddForm, self).update()
File "/usr/lib/python2.7/dist-packages/schooltool/skin/flourish/form.py", line 55, in update
  super(Form, self).update()
File "/usr/lib/python2.7/dist-packages/z3c/form/form.py", line 211, in update
  self.actions.execute()
File "/usr/lib/python2.7/dist-packages/z3c/form/action.py", line 99, in execute
  result = handler()
File "/usr/lib/python2.7/dist-packages/z3c/form/button.py", line 315, in __call__
  return handler(self.form, self.action)
File "/usr/lib/python2.7/dist-packages/z3c/form/button.py", line 170, in __call__
  return self.func(form, action)
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/browser/timetable.py", line 549, in handleAdd
  return form.AddForm.handleAdd.func(self, action)
File "/usr/lib/python2.7/dist-packages/z3c/form/form.py", line 240, in handleAdd
  obj = self.createAndAdd(data)
File "/usr/lib/python2.7/dist-packages/z3c/form/form.py", line 248, in createAndAdd
  self.add(obj)
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/browser/timetable.py", line 584, in add
  schedules[name] = schedule
File "/usr/lib/python2.7/dist-packages/zope/container/btree.py", line 112, in __setitem__
  setitem(self, self._setitemf, key, value)
File "/usr/lib/python2.7/dist-packages/zope/container/contained.py", line 559, in setitem
  notify(event)
File "/usr/lib/python2.7/dist-packages/zope/event/__init__.py", line 31, in notify
  subscriber(event)
File "/usr/lib/python2.7/dist-packages/zope/component/event.py", line 27, in dispatch
  component_subscribers(event, None)
File "/usr/lib/python2.7/dist-packages/zope/component/_api.py", line 139, in subscribers
  return sitemanager.subscribers(objects, interface)
File "/usr/lib/python2.7/dist-packages/zope/interface/registry.py", line 323, in subscribers
  return self.adapters.subscribers(objects, provided)
File "/usr/lib/python2.7/dist-packages/zope/interface/adapter.py", line 601, in subscribers
  subscription(*objects)
File "/usr/lib/python2.7/dist-packages/schooltool/schoolyear/subscriber.py", line 34, in subscriberAdapterDispatcher
  subscriber()
File "/usr/lib/python2.7/dist-packages/schooltool/schoolyear/subscriber.py", line 54, in __call__
  subscriber()
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/calendar.py", line 195, in __call__
  calendar.updateSchedule(container)
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/calendar.py", line 141, in updateSchedule
  schedule_cal = interfaces.IImmutableScheduleCalendar(schedule)
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/timetable/calendar.py", line 80, in __init__
  events = tuple(self.createEvents())
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/calendar.py", line 102, in createEvents
  meetings = schedule.iterMeetings(schedule.first, schedule.last)
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/schedule.py", line 211, in iterMeetings
  meetings = self.iterOriginalMeetings(date, until_date=until_date)
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/schedule.py", line 207, in iterOriginalMeetings
  meetings.extend(list(tt_meetings))
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/schedule.py", line 140, in iterMeetingsInTimezone
  for meeting in meetings:
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/timetable.py", line 194, in iterMeetings
  for orig_meeting in meetings:
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/schedule.py", line 140, in iterMeetingsInTimezone
  for meeting in meetings:
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/schedule.py", line 158, in iterMeetingsWithExceptions
  for original_meeting in meetings:
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/timetable.py", line 71, in iterOriginalMeetings
  self.time_slots.iterDates(dates))
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/daytemplates.py", line 129, in iterDates
  date not in schooldays):
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/app.py", line 184, in __contains__
  for term in self.schoolyear.values():
File "/usr/lib/python2.7/dist-packages/schooltool/timetable/app.py", line 205, in schoolyear
  owner = interfaces.IHaveTimetables(self.schedule)

Modules

schooltool 2.6.3 (/usr/lib/python2.7/dist-packages)
schooltool.cando 2.6.2 (/usr/lib/python2.7/dist-packages)
schooltool.gradebook 2.6.3 (/usr/lib/python2.7/dist-packages)
schooltool.intervention 2.6.2 (/usr/lib/python2.7/dist-packages)
schooltool.lyceum.journal 2.6.3 (/usr/lib/python2.7/dist-packages)

Runtime

Python 2.7.6 (default, Jun 22 2015, 17:58:13)
[GCC 4.8.2]
Linux pcusuario3 3.19.0-51-generic #58~14.04.1-Ubuntu SMP Fri Feb 26 22:02:58 UTC 2016 x86_64 x86_64
Filesystem encoding ANSI_X3.4-1968, preferred ANSI_X3.4-1968