add a python echo server that does not close the connection after each received messages

test/compatibility/python/websockets/echo_server.py

@@ -8,6 +8,7 @@ import websockets
 
 
 async def echo(websocket, path):
+    while True:
         msg = await websocket.recv()
         print(f'Received {len(msg)} bytes')
         await websocket.send(msg)

test/compatibility/python/websockets/echo_server_serve_once.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+
+# WS server example
+
+import asyncio
+import os
+import websockets
+
+
+async def echo(websocket, path):
+    while True:
+        msg = await websocket.recv()
+        print(f'Received {len(msg)} bytes')
+        await websocket.send(msg)
+
+host = os.getenv('BIND_HOST', 'localhost')
+print(f'Serving on {host}:8766')
+
+start_server = websockets.serve(echo, host, 8766, max_size=2 ** 30)
+
+asyncio.get_event_loop().run_until_complete(start_server)
+asyncio.get_event_loop().run_forever()