focus on 3.15 bug fix

Author: sba72

.github/workflows/test-build.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        version: [ '3.15', '3.14' ]
+        version: [ '3.15' ]   # version: [ '3.15', '3.14' ]
         format: [ html, latex ]
     steps:
       - uses: actions/setup-python@master
@@ -26,6 +26,8 @@ jobs:
           ref: ${{ matrix.version }}
       - run: make venv
         working-directory: ./Doc
+      - name: Install rsvg-convert
+        run: sudo apt-get update && sudo apt-get install -y librsvg2-bin
       - uses: actions/checkout@master
         with:
           ref: ${{ matrix.version }}