Description of problem:
When opening a VM in virt-manager I get an error instead of a virt viewer window.

Error launching details: libosinfo: at line 1: Document is empty
 (0)

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/details.py", line 369, in get_instance
    cls._instances[key] = vmmDetails(vm)
  File "/usr/share/virt-manager/virtManager/details.py", line 471, in __init__
    self.init_details()
  File "/usr/share/virt-manager/virtManager/details.py", line 945, in init_details
    self._os_list = vmmOSList()
  File "/usr/share/virt-manager/virtManager/oslist.py", line 39, in __init__
    self._init_state()
  File "/usr/share/virt-manager/virtManager/oslist.py", line 55, in _init_state
    all_os = virtinst.OSDB.list_os()
  File "/usr/share/virt-manager/virtinst/osdict.py", line 225, in list_os
    for name, osobj in self._all_variants.items():
  File "/usr/share/virt-manager/virtinst/osdict.py", line 173, in _all_variants
    loader = self._os_loader
  File "/usr/share/virt-manager/virtinst/osdict.py", line 165, in _os_loader
    loader.process_default_path()
GLib.GError: libosinfo: at line 1: Document is empty
 (0)


Version-Release number of selected component (if applicable):
libosinfo-1.1.0-2.fc28.ppc64le
libvirt-daemon-4.9.0-1.fc28.ppc64le
osinfo-db-20181101-1.fc28.noarch
virt-manager-2.0.0-1.fc28.noarch
virt-viewer-6.0-4.fc28.ppc64le


How reproducible:
100%

Steps to Reproduce:
1. try to open a VM

Additional info:
This is on F-28 ppc64le with the virt-preview repo enabled. It worked fine until a week ago or so.