tornado 5 fixes in tests

- start asyncio loop explicitly in notebook thread (tornado 4 starts per-thread loops automatically, asyncio doesn’t)
- remove unsupported ‘io_loop=‘ arg in websocket test

application runs fine with tornado 5, just a few test bits needed updating

notebook/services/kernels/tests/test_kernels_api.py

@@ -53,11 +53,12 @@ class KernelAPI(object):
 
     def websocket(self, id):
         loop = IOLoop()
+        loop.make_current()
         req = HTTPRequest(
             url_path_join(self.base_url.replace('http', 'ws', 1), 'api/kernels', id, 'channels'),
             headers=self.headers,
         )
-        f = websocket_connect(req, io_loop=loop)
+        f = websocket_connect(req)
         return loop.run_sync(lambda : f)
 
 

notebook/tests/launchnotebook.py

@@ -135,6 +135,9 @@ class NotebookTestBase(TestCase):
 
         started = Event()
         def start_thread():
+            if 'asyncio' in sys.modules:
+                import asyncio
+                asyncio.set_event_loop(asyncio.new_event_loop())
             app = cls.notebook = NotebookApp(
                 port=cls.port,
                 port_retries=0,