Sets the cpu affinity for the supplied processes.
    Requires the optional psutil module.
    :param int n: affinity
    :param list process_ids: a list of pids
    :param bool actual: Test workaround for Travis not supporting cpu affinity

def set_cpu_affinity(n, process_ids, actual=not Conf.TESTING):
    """
    Sets the cpu affinity for the supplied processes.
    Requires the optional psutil module.
    :param int n: affinity
    :param list process_ids: a list of pids
    :param bool actual: Test workaround for Travis not supporting cpu affinity
    """
    # check if we have the psutil module
    if not psutil:
        logger.warning('Skipping cpu affinity because psutil was not found.')
        return
    # check if the platform supports cpu_affinity
    if actual and not hasattr(psutil.Process(process_ids[0]), 'cpu_affinity'):
        logger.warning('Faking cpu affinity because it is not supported on this platform')
        actual = False
    # get the available processors
    cpu_list = list(range(psutil.cpu_count()))
    # affinities of 0 or gte cpu_count, equals to no affinity
    if not n or n >= len(cpu_list):
        return
    # spread the workers over the available processors.
    index = 0
    for pid in process_ids:
        affinity = []
        for k in range(n):
            if index == len(cpu_list):
                index = 0
            affinity.append(cpu_list[index])
            index += 1
        if psutil.pid_exists(pid):
            p = psutil.Process(pid)
            if actual:
                p.cpu_affinity(affinity)
            logger.info(_('{} will use cpu {}').format(pid, affinity))