For me, there are different issues:

* PyType_FromSpec() must fail if a type is declared with Py_TPFLAGS_HAVE_GC but its tp_traverse function is NULL.
* _ssl.SSLError must implement the tp_traverse slot

Moreover, in debug mode, PyObject_GC_Track() calls the traverse function to ensure that it's safe to call it. PyObject_GC_Track() must crash of tp_traverse is NULL. If it didn't track, it means that the _ssl.SSLError instance was not tracked by the GC. Is that ok? Objects implementing the GC protocol should be tracked by the GC, no?

An exception is *likely* to be part of a reference cycle because it contains a traceback which contains frames which contains variables, and one variable can be the exception.