Comment 5 for bug 475148

While breaking the cached reference when a flush occurs might solve this bug, do we really want to invalidate this cache at that point?

Given we've had a number of problems with EventSystem holding references longer than we'd like, might it be worth extending it to use weakrefs to remove this class of problem completely?

Django's signal system behaves this way (the main complication is that bound instance method objects are flyweight, so it needs to reference the instance object and unbound instance method).