Fix ConnectionResetError issues and switch to aiohttp version 3.4.4. Fixes #1474.

gns3server/handlers/api/compute/notification_handler.py

@@ -45,14 +45,14 @@ class NotificationHandler:
         request.app['websockets'].add(ws)
         asyncio.ensure_future(process_websocket(ws))
         with notifications.queue() as queue:
-            while True:
-                try:
+            try:
+                while True:
                     notification = await queue.get_json(1)
                     if ws.closed:
                         break
                     await ws.send_str(notification)
-                except asyncio.futures.CancelledError:
-                    break
-                finally:
-                    request.app['websockets'].discard(ws)
+            finally:
+                if not ws.closed:
+                    await ws.close()
+                request.app['websockets'].discard(ws)
         return ws