I try to create openSUSE 42.2 based appliance at
https://build.opensuse.org/package/show/home:embar-:boo1011147/livecd-gnome

if I change parameter to 

<preferences>
    <type primary="true" boot="isoboot/suse-leap42.2" ...

I see error:

[   53s] Jun-08 03:58:07 <3> : Could not find valid boot image description
for'isoboot/suse-leap42.2'.
[   53s] Jun-08 03:58:07 <3> : The required boot image description:
'isoboot/suse-leap42.2' for the selected build type: 'iso' does not exist.
Jun-08 03:58:07 <3> : KIWI exited with error(s)
[   53s] 
[   53s] Jun-08 03:58:07 <1> : Closing session with ecode: 1


But it success if I set to 

<preferences>
    <type primary="true" boot="isoboot/suse-leap42.1" ...