How do I configure openstack novnc proxy to use SSL/TLS to access instances consoles ?

Issue

• I want to access openstack instances vnc console using SSL/TLS
• Suddenly access to consoles stops working

• I get the following error when I manually execute nova-vnc-proxy in debug mode

   30: 87.124.34.97: new handler Process
   30: handler exception: WSRequestHandler instance has no attribute 'last_code'
   30: Traceback (most recent call last):
    File "/usr/lib/python2.7/site-packages/websockify/websocket.py", line 696, in top_new_client
      self.client = self.do_handshake(startsock, address)
    File "/usr/lib/python2.7/site-packages/websockify/websocket.py", line 628, in do_handshake
      if wsh.last_code == 101:
  AttributeError: WSRequestHandler instance has no attribute 'last_code'