GitLab-CI Kubernetes Variables aren't set?

I'm trying to setup auto deploy with Kubernetes on GitLab. I've successfully enabled Kubernetes integration in my project settings.

Well, the integration icon is green and when I click "Test Settings" I see "We sent a request to the provided URL":

My deployment environment is the Google Container Engine.

Here's the auto deploy section in my gitlab-ci.yml config:

deploy:
  image: registry.gitlab.com/gitlab-examples/kubernetes-deploy
  stage: deploy
  script:
    - export
    - echo CI_PROJECT_ID=$CI_PROJECT_ID
    - echo KUBE_URL=$KUBE_URL
    - echo KUBE_CA_PEM_FILE=$KUBE_CA_PEM_FILE
    - echo KUBE_TOKEN=$KUBE_TOKEN
    - echo KUBE_NAMESPACE=$KUBE_NAMESPACE

    - kubectl config set-cluster "$CI_PROJECT_ID" --server="$KUBE_URL" --certificate-authority="$KUBE_CA_PEM_FILE"
    - kubectl config set-credentials "$CI_PROJECT_ID" --token="$KUBE_TOKEN"
    - kubectl config set-context "$CI_PROJECT_ID" --cluster="$CI_PROJECT_ID" --user="$CI_PROJECT_ID" --namespace="$KUBE_NAMESPACE"
    - kubectl config use-context "$CI_PROJECT_ID"

When I look at the results, the deploy phase fails. This is because all the KUBE variables are empty.

I'm not having much luck with the Kubernetes services beyond this point. Am I missing something?

As it turns out, the Deployment Variables will not materialise unless you have configured and referenced an Environment.

Here's what the .gitlab-ci.yaml file looks like with the environment keyword:

deploy:
  image: registry.gitlab.com/gitlab-examples/kubernetes-deploy
  stage: deploy
  environment: production
  script:
    - export
    - echo CI_PROJECT_ID=$CI_PROJECT_ID
    - echo KUBE_URL=$KUBE_URL
    - echo KUBE_CA_PEM_FILE=$KUBE_CA_PEM_FILE
    - echo KUBE_TOKEN=$KUBE_TOKEN
    - echo KUBE_NAMESPACE=$KUBE_NAMESPACE

    - kubectl config set-cluster "$CI_PROJECT_ID" --server="$KUBE_URL" --certificate-authority="$KUBE_CA_PEM_FILE"
    - kubectl config set-credentials "$CI_PROJECT_ID" --token="$KUBE_TOKEN"
    - kubectl config set-context "$CI_PROJECT_ID" --cluster="$CI_PROJECT_ID" --user="$CI_PROJECT_ID" --namespace="$KUBE_NAMESPACE"
    - kubectl config use-context "$CI_PROJECT_ID"