Try to run quickstart.

.gitlab-ci.yml

 pages:
   script:
-  - sphinx-build -b html source build/html 
-  - mv build/html/ public/
+    - sphinx-quickstart
+          #- sphinx-build -b html source build/html 
+          #- mv build/html/ public/
 
   tags:
-  - sphinx
+    - sphinx
   
   only:
-  - master
+    - master
 
   artifacts:
     paths:
-    - public
+      - public
     expire_in: 5min