Add WeasyPrint dependencies

.github/workflows/build.yml

@@ -14,8 +14,10 @@ jobs:
         with:
           python-version: '3.9'
       - name: Install dependencies
+        # Install dependencies for WeasyPrint (pdf_reports): https://doc.courtbouillon.org/weasyprint/stable/first_steps.html#ubuntu-20-04
         run: |
           python -m pip install --upgrade pip
+          sudo apt-get -y install python3-cffi python3-brotli libpango-1.0-0 libharfbuzz0b libpangoft2-1.0-0
           pip install pytest pytest-cov coveralls
       - name: Test pip installation
         run: |