uvt-simplstreams-libvirt on trusty

uvt-simplestreams-libvirt sync release=trusty
qemu-img: Could not open '/tmp/tmpWlr_bf': Image is not in qcow2 format
qemu-img: Could not open '/tmp/tmpWlr_bf'
Traceback (most recent call last):
  File "/usr/bin/uvt-simplestreams-libvirt", line 27, in <module>
    uvtool.libvirt.simplestreams.main()
  File "/usr/lib/python2.7/dist-packages/uvtool/libvirt/simplestreams.py", line 326, in main
    args.func(args)
  File "/usr/lib/python2.7/dist-packages/uvtool/libvirt/simplestreams.py", line 269, in main_sync
    tmirror.sync(smirror, initial_path)
  File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 88, in sync
    return self.sync_index(reader, path, data, content)
  File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 240, in sync_index
    self.sync(reader, path=epath)
  File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 86, in sync
    return self.sync_products(reader, path, data, content)
  File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 318, in sync_products
    self.insert_item(item, src, target, pgree, ipath_cs)
  File "/usr/lib/python2.7/dist-packages/uvtool/libvirt/simplestreams.py", line 236, in insert_item
    pool_name=LIBVIRT_POOL_NAME
  File "/usr/lib/python2.7/dist-packages/uvtool/libvirt/__init__.py", line 60, in create_volume_from_fobj
    shell=False, close_fds=False)
  File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '[u'qemu-img', u'convert', u'-f', u'qcow2', u'-O', u'qcow2', '/tmp/tmpWlr_bf', '/tmp/tmpg2L2rF']' returned non-zero exit status 1