be conservative about kernel_info implementation

in case kernels don't comply with the message spec by leaving out the language key.

IPython/qt/console/ipython_widget.py

@@ -264,7 +264,7 b' class IPythonWidget(FrontendWidget):'
         """ Handle kernel info replies.
         """
         if not self._guiref_loaded:
-            if rep['content']['language'] == 'python':
+            if rep['content'].get('language') == 'python':
                 self._load_guiref_magic()
             self._guiref_loaded = True