[Zope] Delete the properties and propertysheet defined by ZClass

[Takakazu Tamaki]

Hi, all

On my migration of Zope system, the one of ZClass common propertysheets
has stopped using. So, first I just simply delete the definition of this
propertysheet on ZClass, but namespace of existing ZClass instances seem
to be polluted by old properties which were defined by that
propertysheet. 

Second, get back that propertysheet definition using undo, then I try to
delete the properties and propertysheet on each ZClass instance using
manage_delProperties() and delPropertySheet(). but it was failed.

Does anybody have any idea to clean up properties and propertysheet on
ZClass instance?

The version of Zope is 2.5.1 .

Thanks in advance.

---
kaz