On Fedora 20, libvirt-python 1.2.9-2 is not available, missing a fix for
this bug:
$ yum info --enablerepo=fedora-virt-preview libvirt-python
Installed Packages
Name : libvirt-python
Arch : x86_64
Version : 1.1.3.9
Release : 1.fc20
Size : 1.0 M
Repo : installed
From repo : updates
Available Packages
Name : libvirt-python
Arch : x86_64
Version : 1.2.9
Release : 1.fc20
Size : 225 k
Repo : fedora-virt-preview/20/x86_64
Vdsm requires libvirt-1.2.9, available only via virt-preview repo, but
without libvirt-python-1.2.9-2, we cannot use the new virDomainBlockCopy
api.