virt-manager dependency on libgl1-mesa-glx

I have been ruing KVM on Ubuntu 14.04 successfully for some time. Stuffed up my server this week so decided to start from scratch and use Ubuntu 16.04. I found that I couldn't get virt-manager to run - it kept failing with this error:

Couldn't open libGL.so.1: libGL.so.1: caot open shared object file: No such file or directory

The solution is to install libgl1-mesa-glx and then it works. I'm seeing this message now when it starts but it doesn't seem to stop it ruing so it's not a big problem. I think it's somethgni to do with not having nVidia drivers installed - but this is a headless server not ruing X, so I don't need them.

libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast

Odd that the libgl1-mesa-glx package isn't identified as a dependency for virt-manager. Is it a packaging error, perhaps?