[Zope] ZClasses stub module

[Milos Prudek]

Zope 2.7 prints the following warning during startup:

lib/python/Interface/iclass.py:7: DeprecationWarning: The 
Interface.iclass module is no more.
This is a stub module to allow ZClasses that subclass ObjectManager
to continue to function - please fix your ZClasses (using the 'Subobjects'

Yes, I have ZClasses from Zope 2.5.1. I cannot get rid of them yet. 
According to the CHANGES.txt file, I actually do not need to do anything 
yet - the stub should provide ZClass support for now. However the 
warning above says that I should fix my ZClasses using Subobjects.

What precisely should I do in the Subobjects tab?

-- 
Milos Prudek