apply_async: Use specific queue is queue argument already is a Queue instance. Closes celery/kombu#438

celery/app/routes.py

@@ -9,6 +9,8 @@
 """
 from __future__ import absolute_import
 
+from kombu import Queue
+
 from celery.exceptions import QueueNotFound
 from celery.five import string_t
 from celery.utils import lpmerge
@@ -63,13 +65,14 @@ class Router(object):
             queue = route.pop('queue', None)
 
         if queue:
-            try:
-                Q = self.queues[queue]  # noqa
-            except KeyError:
-                raise QueueNotFound(
-                    'Queue {0!r} missing from CELERY_QUEUES'.format(queue))
-            # needs to be declared by publisher
-            route['queue'] = Q
+            if isinstance(queue, Queue):
+                route['queue'] = queue
+            else:
+                try:
+                    route['queue'] = self.queues[queue]
+                except KeyError:
+                    raise QueueNotFound(
+                        'Queue {0!r} missing from CELERY_QUEUES'.format(queue))
         return route
 
     def lookup_route(self, task, args=None, kwargs=None):