Irc: block when the queue is empty instead of needlessly polling it

Rework Irc.processQueue() to block when the queue is full, and abort if the item "None" is sent to it.
To make sure that the None isn't caught by a full queue or pushed back by other elements, this modifies queue.Queue's underlying deque instance directly.

Closes #459.

classes.py

@@ -179,14 +179,12 @@ class Irc(utils.DeprecatedAttributesObject):
         while True:
             throttle_time = self.serverdata.get('throttle_time', 0.005)
             if not self.aborted.wait(throttle_time):
-                try:
-                    data = self.queue.get_nowait()
+                data = self.queue.get()
+                if data is None:
+                    log.debug('(%s) Stopping queue thread due to getting None as item', self.name)
+                    break
+                elif data:
                     self._send(data)
-                except queue.Empty:
-                    pass
-            else:
-                log.debug('(%s) Stopping queue thread as aborted is set', self.name)
-                break
 
     def connect(self):
         """
@@ -396,6 +394,12 @@ class Irc(utils.DeprecatedAttributesObject):
 
         self.socket.close()
 
+        # Stop the queue thread.
+        if self.queue:
+            # XXX: queue.Queue.queue isn't actually documented, so this is probably not reliable in the long run.
+            self.queue.queue.appendleft(None)
+
+        # Stop the ping timer.
         if self.pingTimer:
             log.debug('(%s) Canceling pingTimer at %s due to disconnect() call', self.name, time.time())
             self.pingTimer.cancel()