Per Jeremy’s reply to another post here, that is a problem with the model URL. I was using google drive and having the same problem. I was able to get around it by using wget from the shell to download the file into the models directory of the app. Then the model needs to be renamed to model.pth or the model_file_name variable will need to be changed.
Also, you will need to update line 34 to use models.resnet50.