In PyType_Ready() if the type object you are readying 
does not explicitly define its tp_base value, it will 
default to use PyBaseObject_Type.

However, this assignment does not INCREF the 
PyBaseObject_Type pointer.  Thus, for heap allocated 
type objects, when the type_dealloc() function is 
called, a DECREF is called on tp_base which can 
eventually cause PyBaseObject_Type refcount go to 0, 
at which point bad things happen.