def set_default_schedule(chronos_job):
    """
    Given a chronos job, return a new job identical to the first, but with the
    schedule replaced with one that will set the job to run now.

    :param chronos_job: a chronos job dictionary suitable for POSTing to
        Chronos
    :returns: the chronos_job parameter, with the 'schedule' field modified to
        a schedule for chronos to run the job now and only once. The interval field
        of the schedule is irrelevant, but required by Chronos.
    """
    chronos_job['schedule'] = 'R1//PT1M'
    return chronos_job