Merge pull request pandas-dev#6045 from y-p/PR_ipython_repr_html

CLN: ipython expects None from _repr_html_ to signal no html repr GH5922

Author: y-p

pandas/core/frame.py

@@ -474,7 +474,8 @@ def _repr_html_(self):
         # behaves badly when outputting an HTML table
         # that doesn't fit the window, so disable it.
         if com.in_qtconsole():
-            raise NotImplementedError('HTML output is disabled in QtConsole')
+            # 'HTML output is disabled in QtConsole'
+            return None
 
         if self._info_repr():
             buf = StringIO(u(""))