Getting rid of Plone4Artists Calendar - migration from Plone 3.3.5 to Plone 4.0.7

I am trying to remove P4Artists Calendar from a Plone 3.3.5 site, to upgrade it to Plone 4.0.7.

I ran a script to remove all int开发者_开发技巧erfaces from all objects, specifically:

'p4a.subtyper.interfaces.ISubtyped',
'p4a.calendar.interfaces.ICalendarEnhanced',
'p4a.calendar.interfaces.IPossibleCalendar',
'p4a.calendar.interfaces.ICalendarConfig',
'p4a.calendar.interfaces.IEventProvider',
'p4a.calendar.interfaces.IEvent',
'p4a.calendar.interfaces.IBasicCalendarSupport',
'p4a.calendar.interfaces.ICalendarSupport'

The script I am using uses zope.interfaces.noLongerProvides to get the objects rid of them. First, I do a catalog search and find the objects with the interface, and then noLongerProvides(object, interface).

After doing that, I am able to remove all of them interfaces, except for 'p4a.calendar.interfaces.IPossibleCalendar'. This interface seems to be applied to all of the Folders and Collections at the site, and when trying to remove them, I get an exception. Does anyone know more of this interface and what is the correct way of getting rid of it?

EDIT:

Here are the error messages generated by my script:

Exception at removeinterfaces for interface p4a.calendar.interfaces.IPossibleCalendar 
Exception type: exceptions.ValueError 
Exception value: Can only remove directly provided interfaces. 
Exception traceback (starting next line):
File "remove-p4a.py", line 53, in removeinterfaces
  noLongerProvides(obj, interface)
File "d:\plone-3.3.5-teste-20110927\zope2\lib\python\zope\interface\declarations.py",line 969, in noLongerProvides
  raise ValueError("Can only remove directly provided interfaces.")

These seem to be interfaces that are only applied on startup via zcml. So the only way to remove them is to remove the product from your setup.

Source: http://svn.plone.org/svn/collective/p4a/p4a.plonecalendar/trunk/p4a/plonecalendar/configure.zcml