The Unpickler forget about its find_class attribute.

Modules/cPickle.c

@@ -5232,6 +5232,7 @@ Unpickler_dealloc(Unpicklerobject *self)
 	Py_XDECREF(self->pers_func);
 	Py_XDECREF(self->arg);
 	Py_XDECREF(self->last_string);
+	Py_XDECREF(self->find_class);
 
 	if (self->marks) {
 		free(self->marks);
@@ -5263,6 +5264,7 @@ Unpickler_traverse(Unpicklerobject *self, visitproc visit, void *arg)
 	VISIT(self->pers_func);
 	VISIT(self->arg);
 	VISIT(self->last_string);
+	VISIT(self->find_class);
 #undef VISIT
 	return 0;
 }
@@ -5279,6 +5281,7 @@ Unpickler_clear(Unpicklerobject *self)
 	CLEAR(self->pers_func);
 	CLEAR(self->arg);
 	CLEAR(self->last_string);
+	CLEAR(self->find_class);
 #undef CLEAR
 	return 0;
 }