Runtime error when websocket is missing from environment

engineio/async_eventlet.py

@@ -1,10 +1,23 @@
 import importlib
+import sys
+
+from eventlet.websocket import WebSocketWSGI as _WebSocketWSGI
+
+
+class WebSocketWSGI(_WebSocketWSGI):  # pragma: no cover
+    def __call__(self, environ, start_response):
+        if 'eventlet.input' not in environ:
+            raise RuntimeError('You need to use the eventlet server. '
+                               'See the Deployment section of the '
+                               'documentation for more information.')
+        super(WebSocketWSGI, self).__call__(environ, start_response)
+
 
 async = {
     'threading': importlib.import_module('eventlet.green.threading'),
     'thread_class': 'Thread',
     'queue': importlib.import_module('eventlet.queue'),
     'queue_class': 'Queue',
-    'websocket': importlib.import_module('eventlet.websocket'),
+    'websocket': sys.modules[__name__],
     'websocket_class': 'WebSocketWSGI'
 }

tests/test_server.py

@@ -90,13 +90,13 @@ def test_async_mode_eventlet(self):
 
         from eventlet.green import threading
         from eventlet import queue
-        from eventlet import websocket
+        from engineio import async_eventlet
 
         self.assertEqual(s.async['threading'], threading)
         self.assertEqual(s.async['thread_class'], 'Thread')
         self.assertEqual(s.async['queue'], queue)
         self.assertEqual(s.async['queue_class'], 'Queue')
-        self.assertEqual(s.async['websocket'], websocket)
+        self.assertEqual(s.async['websocket'], async_eventlet)
         self.assertEqual(s.async['websocket_class'], 'WebSocketWSGI')
 
     @mock.patch('importlib.import_module', side_effect=_mock_import)