Deletes a job.

    :param job_id: unique identifier for this job

    >>> delete_job('http://example.com/test')

def delete_job(job_id, connection=None):
    """Deletes a job.

    :param job_id: unique identifier for this job

    >>> delete_job('http://example.com/test')
    """
    if connection is None:
        connection = r
    with connection.pipeline() as pipe:
        pipe.delete(job_key(job_id))
        pipe.zrem(REDIS_KEY, job_id)
        pipe.execute()