use dict.get(key) instead of dict[key] for pure kernel

This protects against missing keys in object introspection, etc.
when using the pure Python kernel.

closes gh-516
closes gh-519

IPython/core/oinspect.py

@@ -199,7 +199,7 b' def call_tip(oinfo, format_call=True):'
       (regular functions).
     """
     # Get call definition
-    argspec = oinfo['argspec']
+    argspec = oinfo.get('argspec')
     if argspec is None:
         call_line = None
     else:
@@ -218,11 +218,11 b' def call_tip(oinfo, format_call=True):'
 
     # Now get docstring.
     # The priority is: call docstring, constructor docstring, main one.
-    doc = oinfo['call_docstring']
+    doc = oinfo.get('call_docstring')
     if doc is None:
-        doc = oinfo['init_docstring']
+        doc = oinfo.get('init_docstring')
     if doc is None:
-        doc = oinfo['docstring']
+        doc = oinfo.get('docstring','')
 
     return call_line, doc
 

IPython/frontend/qt/console/frontend_widget.py

@@ -355,13 +355,15 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
             # line as string, later we can pass False to format_call and
             # syntax-highlight it ourselves for nicer formatting in the
             # calltip.
-            if rep['content']['ismagic']:
+            content = rep['content']
+            # if this is from pykernel, 'docstring' will be the only key
+            if content.get('ismagic', False):
                 # Don't generate a call-tip for magics. Ideally, we should
                 # generate a tooltip, but not on ( like we do for actual
                 # callables.
                 call_info, doc = None, None
             else:
-                call_info, doc = call_tip(rep['content'], format_call=True)
+                call_info, doc = call_tip(content, format_call=True)
             if call_info or doc:
                 self._call_tip_widget.show_call_info(call_info, doc)
 
@@ -369,7 +371,14 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
         """ Handle display hook output.
         """
         if not self._hidden and self._is_from_this_session(msg):
-            self._append_plain_text(msg['content']['data']['text/plain'] + '\n')
+            data = msg['content']['data']
+            if isinstance(data, basestring):
+                # plaintext data from pure Python kernel
+                text = data
+            else:
+                # formatted output from DisplayFormatter (IPython kernel)
+                text = data.get('text/plain', '')
+            self._append_plain_text(text + '\n')
 
     def _handle_stream(self, msg):
         """ Handle stdout, stderr, and stdin.