Test tempest.api.compute.servers.test_novnc.NoVNCConsoleTestJSON.test_novnc failing often

[Slawek Kaplonski]

I see that Tempest API test tempest.api.compute.servers.test_novnc.NoVNCConsoleTestJSON.test_novnc is failing quite often on tempest-multinode-full and tempest-multinode-full-py3 jobs.
Example: https://logs.opendev.org/12/672612/4/check/tempest-multinode-full-py3/72623e0/testr_results.html.gz

Logstash query which I used to find other occurrences: http://logstash.openstack.org/#dashboard/file/logstash.json?query=message%3A%5C%22AssertionError%3A%20True%20is%20not%20false%20%3A%20Token%20must%20be%20invalid%20because%20the%20connection%20closed.%5C%22

I found 61 entries in last 7 days.