title: Gitlab CI docker cannot login to docker hub
body: <p>i have two project on gitlab with same CI config file and ci variables. When i try to build dockerfile, one project passed, but second say:</p>
  <p><code>Error: Cannot perform an interactive login from a non TTY device</code></p>
  <p>config:</p>
  <pre><code>image: docker:latest
  services:
    - docker:dind
  
  stages:
    - build
    
  variables:
    CONTAINER_IMAGE: sleezy/go-hello-world:${CI_COMMIT_SHORT_SHA}
  
  build:
    stage: build
    script:
      - docker login -u ${DOCKER_USER} -p ${DOCKER_PASSWORD}
      - docker build -t ${CONTAINER_IMAGE} .
      - docker tag ${CONTAINER_IMAGE} ${CONTAINER_IMAGE}
      - docker tag ${CONTAINER_IMAGE} sleezy/go-hello-world:latest
      - docker push ${CONTAINER_IMAGE}
  </code></pre>
  <p>How i said, everything is same, variables, dockerhub account - username, password, config, even gitlab runner version, so i really dont know why? Any help, thanks.</p>