docs: def handle_unexpected_exception(exc):
      # type: (BaseException) -> str
      """Return an error message and write a log file if logging was not enabled.
  
      Args:
          exc: The unexpected exception.
  
      Returns:
          A message to display to the user concerning the unexpected exception.
      """
      try:
          write_logfile()
          addendum = 'Please see the log file for more information.'
      except IOError:
          addendum = 'Unable to write log file.'
      try:
          message = str(exc)
          return '{}{}{}'.format(message, '\n' if message else '', addendum)
      except Exception:  # pylint: disable=broad-except
          return str(exc)