fix Traitlets 4.2 API usage.

Carreau · Carreau · commit f0e1cb1b7e07 · 2016-05-18T10:07:09.000-07:00
diff --git a/IPython/core/extensions.py b/IPython/core/extensions.py
@@ -49,8 +49,7 @@ def load_ipython_extension(ipython):
     is added to ``sys.path`` automatically.
     """
 
-    shell = Instance('IPython.core.interactiveshell.InteractiveShellABC').tag(
-                     allow_none=True)
+    shell = Instance('IPython.core.interactiveshell.InteractiveShellABC', allow_none=True)
 
     def __init__(self, shell=None, **kwargs):
         super(ExtensionManager, self).__init__(shell=shell, **kwargs)
