Try adding pyyaml before script

.gitlab-ci.yml

@@ -8,6 +8,7 @@ cache:
 
 before_script:
   - npm install gitbook-cli -g # install gitbook
+  - npm install pyyaml
   - gitbook fetch 3.2.3 # fetch final stable version
   - gitbook install # add any requested plugins in book.json
 
@@ -23,7 +24,6 @@ test:
 build:
   stage: build
   script:
-    - npm install pyyaml
     - python make_documents.py
     - pandoc Deliverable_4-8.md -f markdown -t docx -s -o Deliverable_4-8.docx
     - pandoc Deliverable_4-9.md -f markdown -t docx -s -o Deliverable_4-9.docx