build the Dockerimage used in CI

.gitlab-ci.yml

-image: quantumtinkerer/research
+image: gitlab.kwant-project.org:5005/qt/adaptive:latest
 
-test:
-  script:
-    - py.test --verbose --cov=adaptive --cov-report term --cov-report html adaptive
-  artifacts:
-    paths:
-      - htmlcov
-
-authors check:
-  script:
-    - MISSING_AUTHORS=$(git shortlog -s HEAD | sed -e "s/^[0-9\t ]*//"| xargs -i sh -c 'grep -q "{}" AUTHORS.md || echo "{} missing from authors"')
-    - if [ ! -z "$MISSING_AUTHORS" ]; then { echo $MISSING_AUTHORS; exit 1; }; fi
-  allow_failure: true
-
-check whitespace style:
-  script: ./check_whitespace
-  allow_failure: true
+stages:
+  - prebuild
+  - test
 
 build docker:
+  stage: prebuild
   image:
     name: gcr.io/kaniko-project/executor:debug
     entrypoint: [""]
   before_script:
-    - docker login -u $CI_DEPLOY_USER -p $CI_DEPLOY_PASSWORD $CI_REGISTRY
+    - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
     - export CI_REF=${CI_COMMIT_TAG:-latest}
   script:
     - /kaniko/executor
@@ -34,3 +22,23 @@ build docker:
       - Dockerfile
       - environment.yml
       - test-requirements.txt
+
+test:
+  stage: test
+  script:
+    - py.test --verbose --cov=adaptive --cov-report term --cov-report html adaptive
+  artifacts:
+    paths:
+      - htmlcov
+
+authors check:
+  stage: test
+  script:
+    - MISSING_AUTHORS=$(git shortlog -s HEAD | sed -e "s/^[0-9\t ]*//"| xargs -i sh -c 'grep -q "{}" AUTHORS.md || echo "{} missing from authors"')
+    - if [ ! -z "$MISSING_AUTHORS" ]; then { echo $MISSING_AUTHORS; exit 1; }; fi
+  allow_failure: true
+
+check whitespace style:
+  stage: test
+  script: ./check_whitespace
+  allow_failure: true