PyTorch tutorial for Neural transfert of artistic style

Thanks for having reported this issue.

The code is working on my computer but anyway, I did it quickly when I discovered Pytorch, so I am not surprised if it causes bugs on another system. It is fool of hacks and the implementation is not clean (as you can see here: How to extract features of an image from a trained model). I have to re-write it, I will do it as soon as I have time for myself.