The EventManager class expects INotifyable objects for addition to its queues. Although it does not force objects to inherit from INotifyable, it will print out a warning, if an object to add does not inherit from this class. Newly created classes thus should inherit from INotifyable, if they do not already inherit from it (by e.g. inheriting from BaseObject).

The eventgrabber attribute of the EventManager was renamed to event_grabber. Make sure, that you replace all occurances of it accordingly, because there is no compatibility support.

The EventManager is a full class by now and does not implement __slots__ anymore. If your classes inherit from it, make sure, that they deal with that change correctly.