allow calling PyType_Ready on already registered pyston types

src/capi/typeobject.cpp

@@ -3402,14 +3402,14 @@ extern "C" void PyType_GiveHcAttrsDictDescr(PyTypeObject* cls) noexcept {
 }
 
 extern "C" int PyType_Ready(PyTypeObject* cls) noexcept {
-    ASSERT(!cls->is_pyston_class, "should not call this on Pyston classes");
-
     // if this type is already in ready state we are finished.
     if (cls->tp_flags & Py_TPFLAGS_READY) {
         assert(cls->tp_dict != NULL);
         return 0;
     }
 
+    ASSERT(!cls->is_pyston_class, "should not call this on Pyston classes");
+
     gc::registerNonheapRootObject(cls, sizeof(PyTypeObject));
 
     // unhandled fields: