Comment 9 for bug 1417288

I noticed this, too. And that it seemed to work with later releases. However this is only half true. Actually that error still exists in the tip of the libvirt tree. There is only on commit that fixed an inconsistency related to the --children option with a note saying it would be nice if we would support deletion of external snapshots one day.

So deletion in Trusty/14.04 (still?) requires to add "--metadata" (only deletes the info but leaves the snapshot file which then has to be removed manually outside libvirt).