Make unit tests compatible with Python < 2.7.

tests/__init__.py

@@ -59,6 +59,11 @@ class RQTestCase(unittest.TestCase):
         # Flush afterwards
         self.testconn.flushdb()
 
+    # Implement assertIsNotNone for Python runtimes < 2.7 or < 3.1
+    if not hasattr(unittest.TestCase, 'assertIsNotNone'):
+        def assertIsNotNone(self, value, *args):
+            self.assertNotEqual(value, None, *args)
+
     @classmethod
     def tearDownClass(cls):
         cls.log_handler.pop_thread()