fix Python actions

Author: gcerar

.github/workflows/gh-pages.yml

@@ -45,7 +45,9 @@ jobs:
           cache: npm
 
       - name: Pull COBISS and ArXiv metadata
-        run: python scripts/cobiss_parser.py
+        run: |
+          python -m pip install arxiv requests unidecode ujson
+          python scripts/cobiss_parser.py
 
       - name: Install NodeJS dependencies
         run: npm ci