use 18-dind service

.gitlab-ci.yml

@@ -12,9 +12,9 @@ ci_test_image:
   stage: build
   variables:
     DOCKER_DRIVER: overlay2
-  image: docker:18
+  image: docker:stable
   services:
-    - docker:dind
+    - docker:18-dind
   before_script:
     - docker info
   script:

test/Dockerfile

@@ -22,4 +22,3 @@ RUN apk --no-cache add \
 COPY ./requirements.txt /requirements.txt
 RUN pip3 install -r /requirements.txt
 RUN ln -s /usr/bin/python3 /usr/bin/python
-