我正在尝试使用aws sdk ruby for amazon elasticmapreduce服务运行一个step，该服务使用hadoop，虽然我可以创建集群和step，但当使用web界面手动设置时，该步骤总是失败

emr = Aws::EMR::Client.new
    cluster_id = "*******"
    resp = emr.add_job_flow_steps({
      job_flow_id: cluster_id, # required
      steps: [ # required
        {
          name: "TestStep", # required
          action_on_failure: "CANCEL_AND_WAIT", # accepts TERMINATE_JOB_FLOW, TERMINATE_CLUSTER, CANCEL_AND_WAIT, CONTINUE
          hadoop_jar_step: { # required
            jar: 'command-runner.jar',
            args:[
                "-files",
                "s3://source123/mapper.py,s3://source123/source_reducer.py",
                "-mapper",
                "mapper.py",
                "-reducer",
                "source_reducer.py",
                "-input",
                "s3://source123/input/",
                "-output",
                "s3://source123/output/"
            ]
          },
        },
      ],
    })

我得到的错误是 Cannot run program "-files" (in directory "."): error=2, No such file or directory 有什么线索吗？