Fix suppression of exception chaining with 'from None'

takluyver · takluyver · commit 8ea23f363ada · 2015-07-09T09:16:01.000-05:00
Closes ipythongh-8618
diff --git a/IPython/core/ultratb.py b/IPython/core/ultratb.py
@@ -985,6 +985,8 @@ def get_chained_exception(exception_value):
             cause = getattr(exception_value, '__cause__', None)
             if cause:
                 return cause
+            if getattr(exception_value, '__suppress_context__', False):
+                return None
             return getattr(exception_value, '__context__', None)
 
         chained_evalue = get_chained_exception(evalue)
