模板中的NoEcho无效

我收到以下错误消息:

$ cfn_nag database/gitlab-rds-psql.cf.yml
{
  "failure_count": 3,
  "violations": [
    {
      "id": "F23",
      "type": "FAIL",
      "message": "RDS instance master user password must be Ref to NoEcho Parameter. Default credentials are not recommended",
      "logical_resource_ids": [
        "GitLabDB"
      ]
    },
    {
      "id": "F24",
      "type": "FAIL",
      "message": "RDS instance master username must be Ref to NoEcho Parameter. Default credentials are not recommended",
      "logical_resource_ids": [
        "GitLabDB"
      ]
    },
    {
      "id": "F22",
      "type": "FAIL",
      "message": "RDS instance should not be publicly accessible",
      "logical_resource_ids": [
        "GitLabDB"
      ]
    }
  ]
}

但我试着在模板中将它设置为NoEcho:true:

  GitLabDB:
    Type: AWS::RDS::DBInstance
    Properties:
      DBInstanceIdentifier: gitlab
      AllocatedStorage: !Ref 'DBAllocatedStorage'
      StorageType: gp2
      DBInstanceClass: !Ref 'DBClass'
      Engine: postgres
      EngineVersion: 9.6.3
      AutoMinorVersionUpgrade: true
      BackupRetentionPeriod: 20
      StorageEncrypted: !Ref EncryptData
      DBName: gitlabhq_production
      MasterUsername: gitlab
      MasterUserPassword: 
        - !GetAtt DBPassword.RandomString
        - NoEcho: true
      DBSubnetGroupName: !Ref GitLabDBSubnetGroup
      DBParameterGroupName: default.postgres9.6
      MultiAZ: !Ref MultiAZ
      VPCSecurityGroups:
        - !Ref GitLabDBEC2SecurityGroup
      Tags:
        - Key: AlwaysOn
          Value: true
        - Key: Name
          Value: GitLabDB