def cleanup_connection_file(self):
        """cleanup connection file *if we wrote it*
        
        Will not raise if the connection file was already removed somehow.
        """
        if self._connection_file_written:
            # cleanup connection files on full shutdown of kernel we started
            self._connection_file_written = False
            try:
                os.remove(self.connection_file)
            except OSError:
                pass