Improve message when KVM is unavailable (conflict with VirtualBox)

[popey]

alan@hal:~$ multipass launch 
failed to launch: ioctl(KVM_CREATE_VM) failed: 16 Device or resource busy       
failed to initialize KVM: Device or resource busy

This is because I have VirtualBox installed (and running) on this machine. I had to kill the VBox processes to allow multipass to run. Perhaps a nicer error message might be useful here?

[townsend2010]

I've looked into this some. That message comes from qemu directly when another hypervisor is already being used. It's same message that is presented when starting qemu by hand or even using virt-manager.

Basically, the failure occurs when the kvm code sends an ioctl to the kvm driver, but the return code is not bubbled all the way up the the qemu process. The only way I see to make the message better is to intercept this exact message string and then output a different message string, but that seems fragile since the original string could change at any time.

[Saviq]

Catching this error message and clearly saying that the problem might be another hypervisor running would help a lot here.