Keep in mind the code in the description is in the compute manager, and the virt driver that's raising the exception may not be the libvirt driver, so you can't bake libvirt-specific things into the error that's being handled in the compute manager code, it will have to be generic enough for other virt drivers to raise the same type of error.
Keep in mind the code in the description is in the compute manager, and the virt driver that's raising the exception may not be the libvirt driver, so you can't bake libvirt-specific things into the error that's being handled in the compute manager code, it will have to be generic enough for other virt drivers to raise the same type of error.