title: Docker composer, constraint - did not find expected key
body: <p>We using docker CE(latest) and docker composer version 3.I have a .yml for for 3 services but I want to constraint grafana to the master of the swarm.
  When adding the constraint I get </p>
  
  <blockquote>
    <p>yaml: line 32: did not find expected key
    Tthe script is this:</p>
  </blockquote>
  
  <pre><code>version: '3'
  services:
    influxdb:
      image: "influxdb:latest"
      volumes:
        - /mount/set/influxdb:/var/lib/influxdb
      ports:
        - "5076:5076"
      networks:
        - production
  
    kapacitor:
      image: "kapacitor:latest"
      environment:
        KAPACITOR_HOSTNAME: kapacitor
        KAPACITOR_INFLUXDB_0_URLS_0: http://influxdb:5086
      volumes:
        - /mount/set/kapacitor:/var/lib/kapacitor
      ports:
        - "9092:9092"
      networks:
        - production
  
    grafana:
      image: "grafana/grafana:latest"
        ports:
          - "7000:7000"
        networks:
          - production
        deploy:
          placement:
            constraints: [node.role == manager]
        volumes:
          - /iSCSIDisk/grafana/grafana.ini:/etc/grafana/grafana.ini
          - /iSCSIDisk/grafana/lib:/var/lib/grafana
        environment:
          GF_SECURITY_ADMIN_PASSWORD: secretsecret
  
        networks:
          production:
            external: true
  </code></pre>
  
  <p>I combed over the script several times and could not find any reason for the error, I may be overlooking something, I checked for non-spaces etc, and could not find anything, I checked other articles regarding the same error, and I don't seem to have any missing brackets or duplicates too. Your help will be much appreciated, thank you. :)</p>