<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def validate(args):
 """ %prog validate outdir genome.fasta Validate current folder after MAKER run and check for failures. Failed batch will be written to a directory for additional work. """

    from jcvi.utils.counter import Counter

    p = OptionParser(validate.__doc__)
    opts, args = p.parse_args(args)

    if len(args) != 2:
        sys.exit(not p.print_help())

    outdir, genome = args
    counter = Counter()

    fsnames, suffix = get_fsnames(outdir)
    dsfile = "{0}{1}/{0}.maker.output/{0}_master_datastore_index.log"
    dslogs = [dsfile.format(x, suffix) for x in fsnames]
    all_failed = []
    for f, d in zip(fsnames, dslogs):
        dslog = DatastoreIndexFile(d)
        counter.update(dslog.scaffold_status.values())
        all_failed.extend([(f, x) for x in dslog.failed])

    cmd = 'tail maker.*.out | grep -c "now finished"'
    n = int(popen(cmd).read())
    assert len(fsnames) == n
    print("ALL jobs have been finished", file=sys.stderr)

    nfailed = len(all_failed)
    if nfailed == 0:
        print("ALL scaffolds are completed with no errors", file=sys.stderr)
        return

    print("Scaffold status:", file=sys.stderr)
    print(counter, file=sys.stderr)
    failed = "FAILED"
    fw = open(failed, "w")
    print("\n".join(["\t".join((f, x)) for f, x in all_failed]), file=fw)
    fw.close()

    nlines = sum(1 for x in open("FAILED"))
    assert nlines == nfailed
    print("FAILED !! {0} instances.".format(nfailed), file=sys.stderr)

    # Rebuild the failed batch
    failed_ids = failed + ".ids"
    failed_fasta = failed + ".fasta"
    cmd = "cut -f2 {0}".format(failed)
    sh(cmd, outfile=failed_ids)
    if need_update((genome, failed_ids), failed_fasta):
        cmd = "faSomeRecords {0} {1} {2}".\
                    format(genome, failed_ids, failed_fasta)
        sh(cmd)