Comment 5 for bug 1784872

I wanted to see the effect myself, so I set up a new system and triggered the issue.
Message is:
"
Unable to connect to libvirt qemu:///system.

Verify that the 'libvirtd' daemon is running.

Libvirt URI is: qemu:///system

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/connection.py", line 1036, in _do_open
    self._backend.open(self._do_creds_password)
  File "/usr/share/virt-manager/virtinst/connection.py", line 144, in open
    open_flags)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 105, in openAuth
    if ret is None:raise libvirtError('virConnectOpenAuth() failed')
libvirtError: Failed to connect socket to '/var/run/libvirt/libvirt-sock': Permission denied
"

The same applies to commandline tools like
$ virsh list
error: failed to connect to the hypervisor
error: Failed to connect socket to '/var/run/libvirt/libvirt-sock': Permission denied

As I assumed - re-logging the user works fine and resolves the issue.