virt KVM test on s390 fails - invalid machine type

[Jeff Lane ]

Executing KVM Test
DEBUG:root:Starting KVM Test
DEBUG:root:No image specified, downloading one now.
WARNING:root:Cloud Image URL not valid: http://cloud-images.ubuntu.com/zesty/current/zesty-server-cloudimg-s390x-disk1.img
WARNING:root: * This means we could not reach the remote file. Retrying with a different filename schema.
DEBUG:root:Acquiring cloud image from: http://cloud-images.ubuntu.com/zesty/current/zesty-server-cloudimg-s390x.img
DEBUG:root:Creating cloud user-data
DEBUG:root:Creating cloud meta-data
I: -input-charset not specified, using utf-8 (detected in locale settings)
Total translation table size: 0
Total rockridge attributes bytes: 331
Total directory bytes: 0
Path table size(bytes): 10
Max brk space used 0
183 extents written (0 MB)
DEBUG:root:Attempting boot for:zesty-server-cloudimg-s390x.img
DEBUG:root:Attaching Cloud config disk
DEBUG:root:Using params:qemu-system-s390x -m 1024 -display none -nographic -net nic -net user,net=10.0.0.0/8,host=10.0.0.1,hostfwd=tcp::2222-:22 -enable-kvm -machine s390-ccw-virtio-2.5 -drive file=zesty-server-cloudimg-s390x.img,if=virtio -drive file=seed.iso,if=virtio
INFO:root:Storing VM console output in /home/ubuntu/.cache/plainbox/sessions/canonical-certification-server-2017-04-17T14.03.47.session/CHECKBOX_DATA/virt_debug
E: KVM instance failed to boot
=============================Console output=============================
qemu-system-s390x: -nographic: unsupported machine type 's390-ccw-virtio-2.5'
Use -machine help to list supported machines

E: KVM instance failed to boot