title: openstack nova-compute Failed to connect to libvirt
body: <p>After interruption of power supply, error message shows up.</p>
  <p>oslo_service.service [-] Error starting thread.: TypeError: Parameterized generics cannot be used with class or instance checks
  nova.virt.libvirt.driver [-] Connection event '0' reason 'Failed to connect to libvirt: Parameterized generics cannot be used with class or instance checks'
  <a href="https://i.stack.imgur.com/DC7TH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DC7TH.png" alt="nova.virt.libvirt.driver [-] Connection event '0' reason 'Failed to connect to libvirt: Parameterized generics cannot be used with class or instance checks'" /></a></p>
  <p>TRY1:
  Restart openstack-nova and libvirtd, still the same.</p>
  <p>TRY2:
  Reinstall openstack-nova libvirt, everything is ok now.</p>