Trouble finding references that are keeping objects alive

[t.mitchell at aranz.com]

More info:
The project has cyclic references to the objects in the projects, but
this should be handled by gc.collect().  Here's is my 'project still
alive' test:

            # store a weakref for debugging
            p = weakref.ref(self.data.project)
            self.data.setProject(None, None)
            gc.collect() # whole project is cyclic
            p = p()
            if p is not None:
                print 'Project still exists!!'

Cheers
Tim