code: def kernel_restarted_message(self, msg):
          
          if not self.is_error_shown:
              # If there are kernel creation errors, jupyter_client will
              # try to restart the kernel and qtconsole prints a
              # message about it.
              # So we read the kernel's stderr_file and display its
              # contents in the client instead of the usual message shown
              # by qtconsole.
              try:
                  stderr = self._read_stderr()
              except Exception:
                  stderr = None
              if stderr:
                  self.show_kernel_error('<tt>%s</tt>' % stderr)
          else:
              self.shellwidget._append_html("<br>%s<hr><br>" % msg,
                                            before_prompt=False)
docs: Show kernel restarted/died messages.