Ever so often I find an old #qemu VM and when starting it I see:
$ virsh start myvm
error: Failed to start domain 'myvm'
error: unsupported configuration: Emulator '/usr/bin/kvm' does not support machine type 'pc-0.12'
(which happens since qemu removed the pc-0.12 machine type a while back)
Now one could fix the domain XML by hand by why not let a script do it? Turns out #Ubuntu shipped one but removed it already. It's still in their version control though: https://git.launchpad.net/ubuntu/+source/libvirt/tree/debian/libvirt-migrate-qemu-machinetype?h=applied/ubuntu/xenial