Working on https://bugzilla.opensuse.org/show_bug.cgi?id=1228659 we found an
ordering issue, where the kernel gets installed before some packages from
systemd.

See comments 27 and 28

Some %post scriptlets will require to execute binaries that come from those
packages, but a partial systemd upgrade makes those binaries from the old
systemd fail because the libraries are updated.

At least there are two packages from systemd that needs to be updated before
the kernel: udev and systemd-boot.

IIUC the order can be fixed with adding in the .spec file this:

Requires: udev
Requires: (systemd-boot if sdbootutil)

or maybe

Requires: (systemd-boot if systemd-boot)