I verified this bug with virt-viewer-5.0-2.el7.x86_64 and libgovirt-0.3.3-5.el7.x86_64.
# remote-viewer --ovirt-ca-file=ca4.crt ovirt://ibm-x3250m5-03.rhts.eng.pek2.redhat.com/rhel7.2 --debug
(remote-viewer:26631): virt-viewer-DEBUG: Opening display to ovirt://ibm-x3250m5-03.rhts.eng.pek2.redhat.com/rhel7.2
(remote-viewer:26631): virt-viewer-DEBUG: oVirt base URI: ibm-x3250m5-03.rhts.eng.pek2.redhat.com
(remote-viewer:26631): virt-viewer-DEBUG: oVirt VM name: rhel7.2
(remote-viewer:26631): libsoup-CRITICAL **: soup_auth_authenticate: assertion 'username != NULL' failed
(remote-viewer:26631): virt-viewer-DEBUG: failed to get oVirt 'api' collection: Cancelled
The authentication dialog can be cancelled successfully.
So move the bug from ON_QA to VERIFIED.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2017:1849