Start process.

def start(self):
        """Start process."""
        logger.debug(str(' '.join(self._cmd_list)))

        if not self._fired:
            self._partial_ouput = None
            self._process.start(self._cmd_list[0], self._cmd_list[1:])
            self._timer.start()
        else:
            raise CondaProcessWorker('A Conda ProcessWorker can only run once '
                                     'per method call.')