PX4 Python HIL using JSBSim

I am trying to use this project:
https://pixhawk.org/users/hil#python_hil
and I have installed as instructed under linux/ubuntu.

When I try to run the script like this:
~/HIL-master$python runhil -h
I get an error:

from pymavlink.mavutil import x25rc

ImportError: No module named mavutil

What am I missing please?

Adrian