def launchWorkerProcesses(self, spawner, protocols, arguments):
        """
        Spawn processes from a list of process protocols.

        @param spawner: A C{IReactorProcess.spawnProcess} implementation.

        @param protocols: An iterable of C{ProcessProtocol} instances.

        @param arguments: Extra arguments passed to the processes.
        """
        workertrialPath = theSystemPath[
            'twisted.trial._dist.workertrial'].filePath.path
        childFDs = {0: 'w', 1: 'r', 2: 'r', _WORKER_AMP_STDIN: 'w',
                    _WORKER_AMP_STDOUT: 'r'}
        environ = os.environ.copy()
        # Add an environment variable containing the raw sys.path, to be used by
        # subprocesses to make sure it's identical to the parent. See
        # workertrial._setupPath.
        environ['TRIAL_PYTHONPATH'] = os.pathsep.join(sys.path)
        for worker in protocols:
            args = [sys.executable, workertrialPath]
            args.extend(arguments)
            spawner(worker, sys.executable, args=args, childFDs=childFDs,
                    env=environ)

        Spawn processes from a list of process protocols.

        @param spawner: A C{IReactorProcess.spawnProcess} implementation.

        @param protocols: An iterable of C{ProcessProtocol} instances.

        @param arguments: Extra arguments passed to the processes.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/_dist/disttrial.py