console: make unsupported ws scheme in python < 2.7.4

Due to a bug in python < 2.7.4, urlparse won't parse a query string
in a URL where the scheme is not recognized:

http://bugs.python.org/issue9374

Commit 1dda5ef75a5c141c316639716820b0c37773a9e3 added some tests for
websocketproxy that uses urlparse to get a token but these don't work
on python < 2.7.4 since the scheme in the tests is "ws://".

In the actual code, raise an exception if python < 2.7.4 and an
unsupported URL scheme is used.

DocImpact: The "getting-started-with-vnc-proxy" page in the
"admin-guide-cloud" docs should be updated with a note that the web
proxy console URLs do not support the websocket protocol scheme (ws://)
on python versions less than 2.7.4.

Change-Id: Ib6e0fc4e50c1ea144a9c538099e23597d66b429b
Closes-Bug: #1376078
Merge "console: make unsupported ws scheme in python < 2.7.4"