I am trying to connect to a Push Topic via the Salesforce Streaming API using Python. My application completes the initial handshake correctly, but then fails on the following connect call, with the error: "403::Unknown client".

My messages work as follows:

Handshake Request

{
    "channel":"/meta/handshake",
    "id":"1",
    "supportedConnectionTypes":["long-polling"],
    "version":"1.0",
    "minimumVersion":"1.0"
}

Handshake Response

{
    "channel":"/meta/handshake",
    "clientId":"xxx",
    "version":"1.0",
    "successful":true,
    "minimumVersion":"1.0",
    "id":"1",
    "supportedConnectionTypes":["long-polling"]
}

It's completed the handshake fine. And then...
Connect Request

{
    "channel":"/meta/connect",
    "clientId":"xxx",
    "id":"2",            
    "connectionType":"long-polling"
}

Connect Response

{
    "channel":"/meta/connect",
    "clientId":"xxx",
    "advice":{
        "reconnect":"handshake",
        "interval":500
    },
    "error":"403::Unknown client",
    "successful":false,
    "id":"2"
}

I have seen this issue here:
https://success.salesforce.com/issues_view?id=a1p30000000T0F0AAK

And read through the documentation, including:
http://www.salesforce.com/developer/docs/api_streaming/Content/DebuggingStreamingAPIApplications.htm

After reading this however, I am no closer to determining what the actual fault or problem is, or how to remedy it.

I have tried a lot of different things and am at a loss at how to get it to work. I am using this Bayeux client library https://github.com/dkmadigan/python-bayeux-client, with some custom amendments to get the authentication working.

Any help would be greatly appreciated.