add RichIPythonWidget._append_latex

shows error in the qtconsole when latex fails

IPython/qt/console/rich_ipython_widget.py

@@ -95,18 +95,17 b' class RichIPythonWidget(IPythonWidget):'
     # 'BaseFrontendMixin' abstract interface
     #---------------------------------------------------------------------------
     def _pre_image_append(self, msg, prompt_number):
-        """ Append the Out[] prompt  and make the output nicer
+        """Append the Out[] prompt  and make the output nicer
 
         Shared code for some the following if statement
         """
-        self.log.debug("execute_result: %s", msg.get('content', ''))
         self._append_plain_text(self.output_sep, True)
         self._append_html(self._make_out_prompt(prompt_number), True)
         self._append_plain_text('\n', True)
 
     def _handle_execute_result(self, msg):
-        """ Overridden to handle rich data types, like SVG.
-        """
+        """Overridden to handle rich data types, like SVG."""
+        self.log.debug("execute_result: %s", msg.get('content', ''))
         if self.include_output(msg):
             self.flush_clearoutput()
             content = msg['content']
@@ -129,24 +128,15 b' class RichIPythonWidget(IPythonWidget):'
                 self._append_html(self.output_sep2, True)
             elif 'text/latex' in data:
                 self._pre_image_append(msg, prompt_number)
-                try:
-                    png = latex_to_png(data['text/latex'], wrap=False)
-                except Exception:
-                    self.log.error("Failed to render latex: %r", data['text/latex'], exc_info=True)
-                    png = None
-                if png is not None:
-                    self._append_png(png, True)
-                    self._append_html(self.output_sep2, True)
-                else:
-                    # Print plain text if png can't be generated
-                    return super(RichIPythonWidget, self)._handle_execute_result(msg)
+                self._append_latex(data['text/latex'], True)
+                self._append_html(self.output_sep2, True)
             else:
                 # Default back to the plain text representation.
                 return super(RichIPythonWidget, self)._handle_execute_result(msg)
 
     def _handle_display_data(self, msg):
-        """ Overridden to handle rich data types, like SVG.
-        """
+        """Overridden to handle rich data types, like SVG."""
+        self.log.debug("display_data: %s", msg.get('content', ''))
         if self.include_output(msg):
             self.flush_clearoutput()
             data = msg['content']['data']
@@ -166,16 +156,7 b' class RichIPythonWidget(IPythonWidget):'
                 jpg = decodestring(data['image/jpeg'].encode('ascii'))
                 self._append_jpg(jpg, True, metadata=metadata.get('image/jpeg', None))
             elif 'text/latex' in data:
-                try:
-                    png = latex_to_png(data['text/latex'], wrap=False)
-                except Exception:
-                    self.log.error("Failed to render latex: %r", data['text/latex'], exc_info=True)
-                    png = None
-                if png is not None:
-                    self._append_png(png, True)
-                else:
-                    # Print plain text if png can't be generated
-                    return super(RichIPythonWidget, self)._handle_display_data(msg)
+                self._append_latex(data['text/latex'], True)
             else:
                 # Default back to the plain text representation.
                 return super(RichIPythonWidget, self)._handle_display_data(msg)
@@ -184,6 +165,18 b' class RichIPythonWidget(IPythonWidget):'
     # 'RichIPythonWidget' protected interface
     #---------------------------------------------------------------------------
 
+    def _append_latex(self, latex, before_prompt=False, metadata=None):
+        """ Append latex data to the widget."""
+        try:
+            png = latex_to_png(latex, wrap=False)
+        except Exception as e:
+            self.log.error("Failed to render latex: '%s'", latex, exc_info=True)
+            self._append_plain_text("Failed to render latex:\n%s\nError was: %s" % (
+                latex, e,
+            ), before_prompt)
+        else:
+            self._append_png(png, before_prompt, metadata)
+
     def _append_jpg(self, jpg, before_prompt=False, metadata=None):
         """ Append raw JPG data to the widget."""
         self._append_custom(self._insert_jpg, jpg, before_prompt, metadata=metadata)