This seems to be working now:
$ qemu-system-x86_64 -drive 'file=http://download.fedoraproject.org/pub/fedora-secondary/releases/29/Server/i386/iso/Fedora-Server-netinst-i386-29-1.2.iso,if=virtio,snapshot=on'
... boots from the ISO image, without error message. So I assume this has been fixed, and I am closing this bug now. If there is anything left to do, feel free to open it again.
This seems to be working now:
$ qemu-system-x86_64 -drive 'file=http:// download. fedoraproject. org/pub/ fedora- secondary/ releases/ 29/Server/ i386/iso/ Fedora- Server- netinst- i386-29- 1.2.iso, if=virtio, snapshot= on'
... boots from the ISO image, without error message. So I assume this has been fixed, and I am closing this bug now. If there is anything left to do, feel free to open it again.