[Libguestfs] failure to virt-sysprep (FC27?)

Since I upgrading to FC27, I *sometimes* fail to virt-sysprep. The debug messages: libguestfs: trace: set_verbose true libguestfs: trace: set_verbose = 0 libguestfs: create: flags = 0, handle = 0x7f4600005dd0, program = python2 libguestfs: trace: set_program "lago" libguestfs: trace: set_program = 0 libguestfs: trace: add_drive_ro "/home/ykaul/ovirt-system-tests/deployment-basic-suite-master/default/images/lago-basic-suite-master-host-0_root.qcow2" libguestfs: trace: add_drive "/home/ykaul/ovirt-system-tests/deployment-basic-suite-master/default/images/lago-basic-suite-master-host-0_root.qcow2" "readonly:true" libguestfs: creating COW overlay to protect original drive content libguestfs: trace: disk_format "/home/ykaul/ovirt-system-tests/deployment-basic-suite-master/default/images/lago-basic-suite-master-host-0_root.qcow2" libguestfs: command: run: qemu-img libguestfs: command: run: \ info libguestfs: command: run: \ --output json libguestfs: command: run: \ /dev/fd/7 qemu-img: Could not open '/dev/fd/7': Failed to get shared "write" lock Is another process using the image? libguestfs: trace: disk_format = NULL (error) libguestfs: trace: add_drive = -1 (error) libguestfs: trace: add_drive_ro = -1 (error) Any ideas? TIA, Y.