message: Fix build failures for python 3.8
  This is a regression caused by
  despite it has been fixed in
diff: @@ -1504,7 +1504,7 @@ static PyTypeObject TFE_Py_Tape_Type = {
  sizeof(TFE_Py_Tape), /* tp_basicsize */
  0, /* tp_itemsize */
  &TFE_Py_Tape_Delete, /* tp_dealloc */
  - nullptr, /* tp_print */
  + 0, /* tp_vectorcall_offset */
  nullptr, /* tp_getattr */
  nullptr, /* tp_setattr */
  nullptr, /* tp_reserved */
  @@ -1542,7 +1542,7 @@ static PyTypeObject TFE_Py_ForwardAccumulator_Type = {
  sizeof(TFE_Py_ForwardAccumulator), /* tp_basicsize */
  0, /* tp_itemsize */
  &TFE_Py_ForwardAccumulatorDelete, /* tp_dealloc */
  - nullptr, /* tp_print */
  + 0, /* tp_vectorcall_offset */
  nullptr, /* tp_getattr */
  nullptr, /* tp_setattr */
  nullptr, /* tp_reserved */
  @@ -1577,7 +1577,7 @@ static PyTypeObject TFE_Py_VariableWatcher_Type = {
  sizeof(TFE_Py_VariableWatcher), /* tp_basicsize */
  0, /* tp_itemsize */
  &TFE_Py_VariableWatcher_Delete, /* tp_dealloc */
  - nullptr, /* tp_print */
  + 0, /* tp_vectorcall_offset */
  nullptr, /* tp_getattr */
  nullptr, /* tp_setattr */
  nullptr, /* tp_reserved */
  