code: def to_css(self):
          
          # TODO should this include the traceback?  any security concerns?
          prefix = self.format_prefix()
          original_error = self.format_original_error()
          sass_stack = self.format_sass_stack()
  
          message = prefix + "\n" + sass_stack + original_error
  
          # Super simple escaping: only quotes and newlines are illegal in css
          # strings
          message = message.replace('\\', '\\\\')
          message = message.replace('"', '\\"')
          # use the maximum six digits here so it doesn't eat any following
          # characters that happen to look like hex
          message = message.replace('\n', '\\00000A')
  
          return BROWSER_ERROR_TEMPLATE.format('"' + message + '"')
docs: Return a stylesheet that will show the wrapped error at the top of
          the browser window.