Merge branch 'release/v0.19.x' into develop

docs/changelog.rst

@@ -46,6 +46,9 @@ Bug fix release.
   constant for use by implementors of :method:`mopidy.local.Library.browse`.
   (Related to: :issue:`833`)
 
+- HTTP frontend: Guard against double close of WebSocket, which causes an
+  :exc:`AttributeError` on Tornado < 3.2.
+
 
 v0.19.3 (2014-08-03)
 ====================

mopidy/http/handlers.py

@@ -110,7 +110,10 @@ class WebSocketHandler(tornado.websocket.WebSocketHandler):
                     self.request.remote_ip, response)
         except Exception as e:
             logger.error('WebSocket request error: %s', e)
-            self.close()
+            if self.ws_connection:
+                # Tornado 3.2+ checks if self.ws_connection is None before
+                # using it, but not older versions.
+                self.close()
 
     def check_origin(self, origin):
         # Allow cross-origin WebSocket connections, like Tornado before 4.0