message: return status in TensorMapDeviceCopy
diff: @@ -58,8 +58,8 @@ static Status TensorMapDeviceCopy(
  for (const std::pair<TensorKey,Tensor>& p : from.tensors()) {
  TensorKey to_key(p.first.dtype());
  Tensor to_val(p.second.dtype());
  - copy(p.first, &to_key);
  - copy(p.second, &to_val);
  + TF_RETURN_IF_ERROR(copy(p.first, &to_key));
  + TF_RETURN_IF_ERROR(copy(p.second, &to_val));
  to->tensors().emplace(to_key, to_val);
  }
  return Status::OK();
  