Update gitlab-ci.yml.

.gitlab-ci.yml

@@ -2,8 +2,10 @@ image: alpine
 
 pages:
   script:
-  - pip3 install -r requirements.txt
-  - pip3 install sphinx
+  - apk add --no-cache python3
+  - python3 -m ensurepip
+  - pip install -r requirements.txt
+  - pip install sphinx
   - apk --no-cache add make
   - cd docs && make html
   - mv build/html/ public/
@@ -12,4 +14,3 @@ pages:
     - public
   only:
   - master
-