[test][worker] Fix Queue import

In Python 3 this module is names queue

beat/core/test/test_worker.py

@@ -36,7 +36,10 @@ logger = logging.getLogger(__name__)
 import unittest
 import simplejson
 import multiprocessing
-import Queue
+try:
+    import Queue
+except ImportError:
+    import queue as Queue
 from time import time
 from time import sleep