Where does --log_prediction_time flag output?

So I’m trying to see what my prediction time is, but I am not sure where it outputs? I can’t seem to find the logs in tensorboard and do not think I see any files in my model directory. This is the command I am running:

onmt-main infer --log_prediction_time --config params.yml --features_file data/train_in.txt > predictions.txt

It is logged in the standard error output, along with the other TensorFlow logs.