uvt-simplestreams-libvirt errors on running sync

[J G]

Running the command produces error, the pool and volume exist.

Pool is created automatically on uvtool-libvirt install, I tried with and without volume, same results.

File are being downloaded into /tmp, then break when the command fails.

openstack@ubuntu:/tmp$ ls -ltrh /tmp
total 812M
-rw------- 1 openstack openstack 0 May 13 17:14 config-err-gHiHvS
-rw------- 1 openstack openstack 246M May 15 08:44 tmp6yyXyz
-rw------- 1 openstack openstack 567M May 15 08:44 tmp0pn66r

openstack@ubuntu:/var/log/libvirt$ uvt-simplestreams-libvirt sync release=trusty arch=amd64
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 70, in create_volume_from_fobj
    pool_name=pool_name
  File "/usr/lib/python2.7/dist-packages/uvtool/libvirt/__init__.py", line 91, in _create_volume_from_fobj_with_size
    vol = pool.createXML(etree.tostring(new_vol), 0)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 2831, in createXML
    if ret is None:raise libvirtError('virStorageVolCreateXML() failed', pool=self)
libvirt.libvirtError: internal error: unable to parse qemu-img output ''