I’ve got the very same problem for the very same repository (NSVF). I tried installing different cuda versions, reinstalling them, linking,… nothing works.
Edit: Ok, this worked for me. Make sure cublas_v2.h is located somewhere on your system, you can use what @ptrblck suggested, i.e find /usr/local/ -name cublas_v2.h If it doesn’t find anything you have to reinstall cuda - I recommend this tutorial Installing CUDA 10.1 on Ubuntu 20.04 | by Stephen Gregory | Medium 24
Do find /usr/local/ -name cublas_v2.h once again to make sure cublas_v2.h is there, if you followed the aforementioned tutorial cublas_v2.h will be in cuda-10-2 folder. No worries, we will symlink it and everything else that is necessary. Just do the following:
sudo ln -s /usr/local/cuda-10.2/targets/x86_64-linux/include/cublas_v2.h /usr/local/cuda-10.1/targets/x86_64-linux/include/cublas_v2.h
and
sudo ln -s /usr/local/cuda-10.2/targets/x86_64-linux/include/cublas_api.h /usr/local/cuda-10.1/targets/x86_64-linux/include/cublas_api.h
You should be good to go. In my case I got:
$ pip install --editable ./
Obtaining file:///home/milos/Projects/repositories/NSVF
Installing collected packages: fairnr
  Running setup.py develop for fairnr
Successfully installed fairnr

Let me know if it works