$ uvt-simplestreams-libvirt -vv sync --source http://cloud-images.ubuntu.com/daily 'supported=True' arch=amd64
Adding: com.ubuntu.cloud.daily:server:12.04:amd64 20160627
Removing: com.ubuntu.cloud.daily:server:12.04:amd64 20160623
Adding: com.ubuntu.cloud.daily:server:15.10:amd64 20160627
Removing: com.ubuntu.cloud.daily:server:15.10:amd64 20160622
Adding: com.ubuntu.cloud.daily:server:16.10:amd64 20160627.1
Removing: com.ubuntu.cloud.daily:server:16.10:amd64 20160626
Adding: com.ubuntu.cloud.daily:server:16.04:amd64 20160627
Removing: com.ubuntu.cloud.daily:server:16.04:amd64 20160625
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 270, in main_sync
    clean_extraneous_images()
  File "/usr/lib/python2.7/dist-packages/uvtool/libvirt/simplestreams.py", line 158, in clean_extraneous_images
    encoded_libvirt_name, pool_name=LIBVIRT_POOL_NAME)
  File "/usr/lib/python2.7/dist-packages/uvtool/libvirt/__init__.py", line 128, in delete_volume_by_name
    volume.delete(flags=0)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 3359, in delete
    if ret == -1: raise libvirtError ('virStorageVolDelete() failed', vol=self)
libvirt.libvirtError: cannot unlink file '/var/lib/uvtool/libvirt/images/x-uvt-b64-Y29tLnVidW50dS5jbG91ZC5kYWlseTpzZXJ2ZXI6MTYuMDQ6YW1kNjQgMjAxNjA2MjU=': Permission denied
ubuntu@diglett:/srv/smoser/curtin/trunk.status$ ls -l /var/lib/uvtool/libvirt/images/x-uvt-b64-Y29tLnVidW50dS5jbG91ZC5kYWlseTpzZXJ2ZXI6MTYuMDQ6YW1kNjQgMjAxNjA2MjU=
-rw------- 1 libvirt-qemu kvm 998572032 Jun 27 15:32 /var/lib/uvtool/libvirt/images/x-uvt-b64-Y29tLnVidW50dS5jbG91ZC5kYWlseTpzZXJ2ZXI6MTYuMDQ6YW1kNjQgMjAxNjA2MjU=