I'm now getting following logs after following your instructions..

libguestfs-test-tool
     ************************************************************
     *                    IMPORTANT NOTICE
     *
     * When reporting bugs, include the COMPLETE, UNEDITED
     * output below in your bug report.
     *
     ************************************************************
PATH=/bin:/sbin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/sbin:/usr/local/bin
SELinux: sh: getenforce: command not found
guestfs_get_append: (null)
guestfs_get_autosync: 1
guestfs_get_backend: direct
guestfs_get_backend_settings: []
guestfs_get_cachedir: /var/tmp
guestfs_get_direct: 0
guestfs_get_hv: /usr/bin/kvm
guestfs_get_memsize: 768
guestfs_get_network: 0
guestfs_get_path: /usr/local/lib/guestfs
guestfs_get_pgroup: 0
guestfs_get_program: libguestfs-test-tool
guestfs_get_recovery_proc: 1
guestfs_get_selinux: 0
guestfs_get_smp: 1
guestfs_get_tmpdir: /tmp
guestfs_get_trace: 0
guestfs_get_verbose: 1
host_cpu: powerpc64
Launching appliance, timeout set to 600 seconds.
libguestfs: launch: program=libguestfs-test-tool
libguestfs: launch: version=1.26.1
libguestfs: launch: backend registered: unix
libguestfs: launch: backend registered: uml
libguestfs: launch: backend registered: direct
libguestfs: launch: backend=direct
libguestfs: launch: tmpdir=/tmp/libguestfscN7Ta1
libguestfs: launch: umask=0002
libguestfs: launch: euid=1000
libguestfs: [00000ms] begin building supermin appliance
libguestfs: [00000ms] run supermin
libguestfs: command: run: /usr/bin/supermin
libguestfs: command: run: \ --build
libguestfs: command: run: \ --verbose
libguestfs: command: run: \ --if-newer
libguestfs: command: run: \ --lock /var/tmp/.guestfs-1000/lock
libguestfs: command: run: \ --copy-kernel
libguestfs: command: run: \ -f ext2
libguestfs: command: run: \ --host-cpu powerpc64
libguestfs: command: run: \ /usr/local/lib/guestfs/supermin.d
libguestfs: command: run: \ -o /var/tmp/.guestfs-1000/appliance.d
supermin: version: 5.1.8
supermin: package handler: debian/dpkg
supermin: acquiring lock on /var/tmp/.guestfs-1000/lock
supermin: if-newer: output does not need rebuilding
libguestfs: [00014ms] finished building supermin appliance
libguestfs: [00014ms] begin testing qemu features
libguestfs: command: run: /usr/bin/kvm
libguestfs: command: run: \ -display none
libguestfs: command: run: \ -help
libguestfs: command: run: /usr/bin/kvm
libguestfs: command: run: \ -display none
libguestfs: command: run: \ -version
libguestfs: qemu version 1.4
libguestfs: command: run: /usr/bin/kvm
libguestfs: command: run: \ -display none
libguestfs: command: run: \ -machine accel=kvm:tcg
libguestfs: command: run: \ -device ?
libguestfs: [00072ms] finished testing qemu features
[00073ms] /usr/bin/kvm \
    -global virtio-blk-pci.scsi=off \
    -nodefconfig \
    -enable-fips \
    -nodefaults \
    -display none \
    -M pseries \
    -machine accel=kvm:tcg \
    -m 768 \
    -no-reboot \
    -rtc driftfix=slew \
    -global kvm-pit.lost_tick_policy=discard \
    -kernel /var/tmp/.guestfs-1000/appliance.d/kernel \
    -initrd /var/tmp/.guestfs-1000/appliance.d/initrd \
    -device virtio-scsi-pci,id=scsi \
    -drive file=/tmp/libguestfscN7Ta1/scratch.1,cache=unsafe,format=raw,id=hd0,if=none \
    -device scsi-hd,drive=hd0 \
    -drive file=/var/tmp/.guestfs-1000/appliance.d/root,snapshot=on,id=appliance,cache=unsafe,if=none \
    -device scsi-hd,drive=appliance \
    -device virtio-serial-pci \
    -serial stdio \
    -chardev socket,path=/tmp/libguestfscN7Ta1/guestfsd.sock,id=channel0 \
    -device virtserialport,chardev=channel0,name=org.libguestfs.channel.0 \
    -append 'panic=1 console=ttyS0 udevtimeout=600 no_timer_check acpi=off printk.time=1 cgroup_disable=memory root=/dev/sdb selinux=0 guestfs_verbose=1 TERM=xterm'
qemu: fatal: This KVM version does not support PAPR

NIP 0000000000000000   LR 0000000000000000 CTR 0000000000000000 XER 0000000000000000
MSR 0000000000000000 HID0 0000000000000000  HF 0000000000000000 idx 0
TB 00000000 00000000 DECR 00000000
GPR00 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR04 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR08 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR12 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR16 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR28 0000000000000000 0000000000000000 0000000000000000 0000000000000000
CR 00000000  [ -  -  -  -  -  -  -  -  ]             RES 0000000000000000
FPR00 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR04 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR08 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR12 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR16 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR20 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR24 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR28 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPSCR 0000000000000000
 SRR0 0000000000000000  SRR1 0000000000000000    PVR 0000000080400010 VRSAVE 0000000000000000
SPRG0 0000000000000000 SPRG1 0000000000000000  SPRG2 0000000000000000  SPRG3 0000000000000000
SPRG4 0000000000000000 SPRG5 0000000000000000  SPRG6 0000000000000000  SPRG7 0000000000000000
CSRR0 0000000000000000 CSRR1 0000000000000000 MCSRR0 0000000000000000 MCSRR1 0000000000000000
  TCR 0000000000000000   TSR 0000000000000000    ESR 0000000000000000   DEAR 0000000000000000
  PIR 0000000000000000 DECAR 0000000000000000   IVPR 0000000000000000   EPCR 0000000000000000
 MCSR 0000000000000000 SPRG8 0000000000000000    EPR 0000000000000000
 MCAR 0000000000000000  PID1 0000000000000000   PID2 0000000000000000    SVR 0000000000000000
 MAS0 0000000000000000  MAS1 0000000000000000   MAS2 0000000000000000   MAS3 0000000000000000
 MAS4 0000000000000000  MAS6 0000000000000000   MAS7 0000000000000000    PID 0000000000000000
MMUCFG 0000000000000000 TLB0CFG 0000000004110200 TLB1CFG 00000000401cc040
libguestfs: error: appliance closed the connection unexpectedly, see earlier error messages
libguestfs: child_cleanup: 0x10016848: child process died
libguestfs: sending SIGTERM to process 30722
libguestfs: error: /usr/bin/kvm killed by signal 6 (Aborted), see debug messages above
libguestfs: error: guestfs_launch failed, see earlier error messages
libguestfs-test-tool: failed to launch appliance
libguestfs: closing guestfs handle 0x10016848 (state 0)
libguestfs: command: run: rm
libguestfs: command: run: \ -rf /tmp/libguestfscN7Ta1