AnerrorwasreportedwhileclosingthewebsocketconnectionfailedInvalidframeheader

I use django and dwebsocket. There is a warning in my browser console. Also it runs well. There is no problem :). But i wondered.

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views.py

import threading
from django.shortcuts import render_to_response
from dwebsocket.decorators import accept_websocket

def index(request):
    return render_to_response('index.html', {})

clients = []

@accept_websocket
def echo(request):
    if request.is_websocket:
        lock = threading.RLock()
        try:
            lock.acquire()
            clients.append(request.websocket)
            for message in request.websocket:
                if not message:
                    break
                for client in clients:
                    client.send(message)
        finally:
            clients.remove(request.websocket)
            lock.release()