Comment # 1 on bug 1191260 from Fabian Vogt

The previous %post always did exit 0:

# vim: set sts=4 sw=4 ts=8 noet:
if ! command -v mokutil >/dev/null; then
        exit 0
fi
# Only apply CA check on the kernel package certs (bsc#1173115)
if [ 0 = 0 ] && mokutil -h | grep -q "ca-check"; then
        MOK_ARG="--ca-check"
else
        MOK_ARG=""
fi
# XXX: Only call mokutil if UEFI and shim are used
for cert in 1AA60533; do
        cert="/etc/uefi/certs/${cert}.crt"
        if ! mokutil --import "$cert" --root-pw ${MOK_ARG}; then
                echo "Failed to import $cert"
        fi
done
exit 0

exit 0

There's also a failure inside OBS builds:

[  162s] (183/197) Installing: kernel-kvmsmall-5.14.8-1.1.x86_64
[..............done]
[  162s] Additional rpm output:
[  162s] Please run "/usr/bin/dracut -f /boot/initrd-5.14.8-1-kvmsmall
5.14.8-1-kvmsmall" as soon as your system is complete.
[  162s] You may need to setup and install the boot loader using the
[  162s] available bootloader for your platform (e.g. grub, lilo, zipl, ...).
[  162s] warning: %post(kernel-kvmsmall-5.14.8-1.1.x86_64) scriptlet failed,
exit status 1

That doesn't show the cause for the non-zero exit directly though.