bpo-31294: Fix ZeroMQSocketListener and ZeroMQSocketHandler examples (#3229)

* Fix ZeroMQSocketListener and ZeroMQSocketHandler examples

* Use send_json and recv_json to simplify pyzmq interfacing

* Add News entry

Doc/howto/logging-cookbook.rst

@@ -1258,8 +1258,8 @@ socket is created separately and passed to the handler (as its 'queue')::
 
     class ZeroMQSocketHandler(QueueHandler):
         def enqueue(self, record):
-            data = json.dumps(record.__dict__)
-            self.queue.send(data)
+            self.queue.send_json(record.__dict__)
+
 
     handler = ZeroMQSocketHandler(sock)
 
@@ -1272,11 +1272,10 @@ data needed by the handler to create the socket::
             self.ctx = ctx or zmq.Context()
             socket = zmq.Socket(self.ctx, socktype)
             socket.bind(uri)
-            QueueHandler.__init__(self, socket)
+            super().__init__(socket)
 
         def enqueue(self, record):
-            data = json.dumps(record.__dict__)
-            self.queue.send(data)
+            self.queue.send_json(record.__dict__)
 
         def close(self):
             self.queue.close()
@@ -1292,12 +1291,13 @@ of queues, for example a ZeroMQ 'subscribe' socket. Here's an example::
         def __init__(self, uri, *handlers, **kwargs):
             self.ctx = kwargs.get('ctx') or zmq.Context()
             socket = zmq.Socket(self.ctx, zmq.SUB)
-            socket.setsockopt(zmq.SUBSCRIBE, '')  # subscribe to everything
+            socket.setsockopt_string(zmq.SUBSCRIBE, '')  # subscribe to everything
             socket.connect(uri)
+            super().__init__(socket, *handlers, **kwargs)
 
         def dequeue(self):
-            msg = self.queue.recv()
-            return logging.makeLogRecord(json.loads(msg))
+            msg = self.queue.recv_json()
+            return logging.makeLogRecord(msg)
 
 
 .. seealso::

Misc/ACKS

@@ -1561,6 +1561,7 @@ Martin Teichmann
 Gustavo Temple
 Mikhail Terekhov
 Victor Terrón
+Pablo Galindo
 Richard M. Tew
 Tobias Thelen
 Christian Theune

Misc/NEWS.d/next/Documentation/2017-09-07-20-49-09.bpo-31294.WgI18w.rst

+Fix incomplete code snippet in the ZeroMQSocketListener and
+ZeroMQSocketHandler examples and adapt them to Python 3.