'with' statement for PubSub (#765)

PubSub objects are now context managers.

redis/client.py

@@ -3339,6 +3339,12 @@ def __init__(self, connection_pool, shard_hint=None,
             ]
         self.reset()
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.reset()
+
     def __del__(self):
         try:
             # if this object went out of scope prior to shutting down

tests/test_pubsub.py

@@ -448,6 +448,15 @@ def test_pattern_message_handler(self, r):
                                                  new_data,
                                                  pattern=self.pattern)
 
+    def test_context_manager(self, r):
+        with r.pubsub() as pubsub:
+            pubsub.subscribe('foo')
+            assert pubsub.connection is not None
+
+        assert pubsub.connection is None
+        assert pubsub.channels == {}
+        assert pubsub.patterns == {}
+
 
 class TestPubSubRedisDown(object):