Sanic support: buggy request parsing

[MarSoft]

When trying to use websocket support with git version of Sanic, I had a problem: server kept responding with 400 Bad request when the browser tried to upgrade connection to websocket.
In the logs I saw the following:

WARNING:engineio:Invalid session 060c95b4c0d54ba5b95665acf1ed751d?EIO=3

Turned out that engineio.AsyncServer.handle_request got two values for sid, first of which is the wrong and second is correct.
Next, QUERY_STRING was taken from the output of self._async['translate_request']. And Sanic-specific implementation turned out to be buggy.

In engineio.async_sanic.translate_request function (line 46) it takes request.url and conditionally appends request.query_string to it. But according to Sanic docs, request.url holds "The full URL of the request, ie: http://localhost:8000/posts/1/?foo=bar"
This bug resulted in query-string being duplicated and URL being treated like this:
'http://localhost:8000/socket.io/?EIO=3&transport=polling&t=LhzFKOB&sid=c0a70e70d8bc465e9611f5bae89ce083?EIO=3&transport=polling&t=LhzFKOB&sid=c0a70e70d8bc465e9611f5bae89ce083 - notice the duplication.

I will now propose the trivial fix as a pull request.

[miguelgrinberg]

Thanks for the detailed description.

Turns out they have changed the way request.url works just a few days ago, in this commit: sanic-org/sanic@1fbde87. That used to be just the path portion of the URL, now they have changed it to the full URL, and if you just want the path, that's request.path. Oh well...

Thanks again. I'll go ahead and merge your change, but I'll hold off on a release, since the current release works well with the 0.4.x releases of sanic and this change will break those. What a mess.