Revert r86726. Sorry about interfering with the rc.

Objects/setobject.c

@@ -1858,7 +1858,7 @@ set_contains(PySetObject *so, PyObject *key)
         tmpkey = make_new_set(&PyFrozenSet_Type, key);
         if (tmpkey == NULL)
             return -1;
-        rv = set_contains_key(so, tmpkey);
+        rv = set_contains(so, tmpkey);
         Py_DECREF(tmpkey);
     }
     return rv;