docs: def generate_plaintext_traceback(self):
          """Like the plaintext attribute but returns a generator"""
          yield text_('Traceback (most recent call last):')
          for frame in self.frames:
              yield text_('  File "%s", line %s, in %s' % (
                  frame.filename,
                  frame.lineno,
                  frame.function_name
                  ))
              yield text_('    ' + frame.current_line.strip())
          yield text_(self.exception)