avoid using borrowed references for PyPy in __Pyx_unpack_tuple2() utility function

--HG--
extra : rebase_source : c458b30a48dfe984ddac7b5e939e01d31f0c458b

Cython/Utility/ObjectHandling.c

@@ -119,10 +119,17 @@ static CYTHON_INLINE int __Pyx_unpack_tuple2(PyObject* tuple, PyObject** pvalue1
             __Pyx_UnpackTupleError(tuple, 2);
             goto bad;
         }
+#if CYTHON_COMPILING_IN_PYPY
+        value1 = PySequence_GetItem(tuple, 0);
+        if (unlikely(!value1)) goto bad;
+        value2 = PySequence_GetItem(tuple, 1);
+        if (unlikely(!value2)) goto bad;
+#else
         value1 = PyTuple_GET_ITEM(tuple, 0);
         value2 = PyTuple_GET_ITEM(tuple, 1);
         Py_INCREF(value1);
         Py_INCREF(value2);
+#endif
         if (decref_tuple) { Py_DECREF(tuple); }
     }
     *pvalue1 = value1;