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- Remove dependencies on ``zope.container``. Instead import
``Object*Event`` classes from ``zope.lifecycleevent`` and import
``IContained`` from ``zope.location``. In order to be able to do
this, depend on ``zope.lifecycleevent``>=3.5.2 and
``zope.location``>=3.5.4.
- Remove a dependency on ``zope.container.contained.Contained``
(this is a dumb base class that defines __parent__ and __name__
as None and declares that the class implements IContained).