Cannot open Instance Console - Failed to connect to server (code: 1006)

Issue

• Console for the instances will fail to connect intermittently
• When a failure is encountered, the following error message will be displayed in the VNC applet:

 Failed to connect to server (code: 1006)

• The following error also appears in /var/log/nova/nova-novncproxy.log

2015-09-03 15:30:16.837 25082 INFO nova.console.websocketproxy [req-bd95c208-68fa-42b4-ad3b-adb2fb7be91c None] Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/websockify/websocket.py", line 711, in top_new_client
    self.new_client()
  File "/usr/lib/python2.7/site-packages/nova/console/websocketproxy.py", line 177, in new_client
    self.new_websocket_client()
  File "/usr/lib/python2.7/site-packages/nova/console/websocketproxy.py", line 117, in new_websocket_client
    tsock = self.socket(host, port, connect=True)
  File "/usr/lib/python2.7/site-packages/websockify/websocket.py", line 180, in socket
    socket.IPPROTO_TCP, flags)
gaierror: [Errno -2] Name or service not known