message: Update cnn_scorer.cpp
diff: @@ -113,6 +113,9 @@ CNNScorer::CNNScorer(const cnn_options& opts)
  if (!net->has_blob("output")) {
  throw usage_error("Model must have output layer named \"output\".");
  }
  + if (!net->has_blob("loss")) {
  + throw usage_error("Model must have loss calculation layer named \"loss\" (to compute gradient for optimization).");
  + }
  if (net->blob_by_name("output")->count() != 2 * bsize) {
  throw usage_error(
  "Model output layer does not have exactly two outputs.");
  