'Open a VNC tunnel to the provided node and return the VNC url.
:param node: Node to open the VNC tunnel to.
:type node: :class:`libcloud.compute.base.Node`
:return: URL of the opened VNC tunnel.
:rtype: ``str``'

def ex_open_vnc_tunnel(self, node):

    path = ('/servers/%s/action/' % node.id)
    response = self._perform_action(path=path, action='open_vnc', method='POST').object
    vnc_url = response['vnc_url']
    return vnc_url
