Show info about the existing crawler jobs.

def list_jobs(tail):
    """Show info about the existing crawler jobs."""
    query = (
        db.session.query(models.CrawlerJob)
        .order_by(models.CrawlerJob.id.desc())
    )
    if tail != 0:
        query = query.limit(tail)

    results = query.yield_per(10).all()
    _show_table(results=results)