title: './docker-compose.yml', service must be a mapping, not a NoneType
body: <p>When I ran: <code>COMPOSE_PROJECT_NAME=zk_test docker-compose up</code>, I got error saying </p>
  
  <blockquote>
    <p>"ERROR: In file './docker-compose.yml', service must be a mapping, not
    a NoneType.".</p>
  </blockquote>
  
  <p>This is my yml file:</p>
  
  <pre><code>version: '2'
  services:
  zoo1:
  image: zookeeper
  restart: always
  container_name: zoo1
  ports:
  - "2181:2181"
  environment:
  ZOO_MY_ID: 1
  ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
  
  zoo2:
  image: zookeeper
  restart: always
  container_name: zoo2
  ports:
  - "2182:2181"
  environment:
  ZOO_MY_ID: 2
  ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
  
  zoo3:
  image: zookeeper
  restart: always
  container_name: zoo3
  ports:
  - "2183:2181"
  environment:
  ZOO_MY_ID: 3
  ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
  </code></pre>
  
  <p>Sample Image:</p>
  
  <p><a href="https://i.stack.imgur.com/8Nyhj.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/8Nyhj.jpg" alt="Sample Image"></a></p>