I think the leak happens when we invoke GC while the recursion limit is exceeded. It goes way if make this change:


    def recurse_in_body_and_except():
        try:
            recurse_in_body_and_except()
        except RecursionError as e:
            gc.disable()
            recurse_in_body_and_except()
            gc.enable()


I also added a __del__ to B and saw it being called when recursion limit is small (though adding the __del__ makes the leak go away. Actually just adding "def f(): pass" is enough to make it go away).