message: More descriptive error message for Concat.
diff: @@ -75,7 +75,9 @@ Status Concat(const gtl::ArraySlice<Tensor>& tensors, Tensor* result) {
  for (int i = 1; i < tensors.size(); ++i) {
  if (tensors[i].dtype() != dtype) {
  return errors::InvalidArgument(
  - "Cannot concatenate tensors that have different data types");
  + "Cannot concatenate tensors that have different data types.", " Got ",
  + DataTypeString(dtype), " and ", DataTypeString(tensors[i].dtype()),
  + ".");
  }
  }
  *result = Tensor(dtype, shape);
  