There is a version mismatch.  Your installed CUDA version is 9.1.  However, your PyTorch package is compiled with CUDA 9.0.
Possible solutions:

Install CUDA 9.0 instead of 9.1, or,
Install PyTorch that is compiled with CUDA 9.1, if there isn’t one yet, you may need download PyTorch source code and compile by yourself.

BTW, I myself failed install PyTorch with Anaconda Python 3.7, but succeeded with 3.6. (on Ubuntu 18.04)
Hope this helps.