VUnit does not handle file permission exception

[std-max]

When I was running VUnit, I got the following error (with WSL)
PermissionError: [Errno 13] Permission denied: '/mnt/c/Windows/system32/config/systemprofile/AppData/Local/Microsoft/WindowsApps/vsim'

At the start of a run.py script, VUnit checks for the available simulators by looking into each path in the PATH variable.
However, sometimes we do not have permission to read a path. And it fails :'(

I will file a PR today.