I get a lot of, e.g.:
Oct 25 13:11:19 peregrine libvirtd[37222]: Cannot get interface flags on 'virbr0': No such device
Oct 25 13:11:19 peregrine firewalld[1106]: ERROR: UNKNOWN_INTERFACE: 'virbr0' is not in any zone
Oct 25 13:11:19 peregrine libvirtd[37222]: error destroying network device virbr0: No such device
Oct 25 21:56:12 peregrine libvirtd[49984]: Cannot get interface flags on 'virbr0': No such device
Oct 25 21:56:12 peregrine firewalld[1106]: ERROR: UNKNOWN_INTERFACE: 'virbr0' is not in any zone
Oct 25 21:56:12 peregrine libvirtd[49984]: error destroying network device virbr0: No such device
Which doesn't tell me anything I don't already know.