Guestfs tools, virt-v2v etc fail to run with the error:

virt-v2v: error: libguestfs error: could not create appliance through libvirt. Original error from libvirt: Cannot find 'passt' in path: No such file or directory [code=38 int1=2]

This problem was found in Fedora recently, and the reason for it is explained here:

https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/YDHKKQSDURTMSKSN6GW3QGQI43DTFXNH/

Dan Berrange worked out what's happening here.

In libguestfs 1.57.1 we checked for passt at runtime, and fell back to
the older (SLIRP) method of user networking. So the test would still
have worked even though passt was not installed.

In libguestfs 1.57.4 we now assume that passt is installed. So now
the test is failed because passt is not installed.

I'll need to add a Requires on passt (to libguestfs).

Currently it is possible to uninstall passt which breaks everything, so we have to make that a hard Requires instead of Recommends.