From b5e7ce30ca9736bbed8af2f6e6086673394fdd79 Mon Sep 17 00:00:00 2001
From: Min RK <benjaminrk@gmail.com>
Date: Wed, 12 Nov 2014 11:29:10 -0800
Subject: [PATCH] handle setting Widget.comm = None

which is done in `Widget.close`

fixes loads of warnings in widget test output, caused every time a widget is closed.
---
 IPython/html/widgets/widget.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/IPython/html/widgets/widget.py b/IPython/html/widgets/widget.py
index 0eccf42f5..5a398fc35 100644
--- a/IPython/html/widgets/widget.py
+++ b/IPython/html/widgets/widget.py
@@ -175,7 +175,8 @@ class Widget(LoggingConfigurable):
 
     def _comm_changed(self, name, new):
         """Called when the comm is changed."""
-        self.comm = new
+        if new is None:
+            return
         self._model_id = self.model_id
         
         self.comm.on_msg(self._handle_msg)