在arch上用virt-manager安装虚拟机失败，最后给我的错误提示是

Unable to complete install: 'Cannot set property Before, or unknown property.'

details：
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 90, in cb_wrapper

callback(asyncjob, *args, **kwargs)

File "/usr/share/virt-manager/virtManager/create.py", line 2277, in _do_async_install

guest.start_install(meter=meter)

File "/usr/share/virt-manager/virtinst/guest.py", line 501, in start_install

noboot)

File "/usr/share/virt-manager/virtinst/guest.py", line 416, in _create_guest

dom = self.conn.createLinux(start_xml or final_xml, 0)

File "/usr/lib/python2.7/site-packages/libvirt.py", line 3606, in createLinux

if ret is None:raise libvirtError('virDomainCreateLinux() failed', conn=self)

libvirtError: Cannot set property Before, or unknown property.