Address some more review comments...

IPython/html/tests/widgets/manager.js

@@ -27,7 +27,7 b' casper.notebook_test(function () {'
 
     index = this.append_cell(
         'from IPython.html.widgets import Widget\n' + 
-        'widget = Widget.widgets.values()[0]\n' +
+        'widget = list(Widget.widgets.values())[0]\n' +
         'print(widget.model_id)');
     this.execute_cell_then(index, function(index) {
         var output = this.get_output_cell(index).text.trim();

IPython/html/widgets/widget.py

@@ -101,8 +101,7 b' class Widget(LoggingConfigurable):'
         """Static method, called when a widget is constructed."""
         target_name = msg['content']['data']['target_name']
         widget_class = import_item(target_name)
-        widget = widget_class(open_comm=False)
-        widget.comm = comm
+        widget = widget_class(comm=comm)
 
 
     #-------------------------------------------------------------------------
@@ -141,7 +140,6 b' class Widget(LoggingConfigurable):'
         super(Widget, self).__init__(**kwargs)
 
         Widget._call_widget_constructed(self)
-        if open_comm:
             self.open()
 
     def __del__(self):