specify py version as string in workflow

Author: rgaudin

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       max-parallel: 3
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9, 3.10]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
     steps:
       - name: install ffmpeg and gifsicle
         run: sudo apt update && sudo apt install ffmpeg gifsicle
@@ -43,7 +43,7 @@ jobs:
     - name: Set up Python 3.8
       uses: actions/setup-python@v1
       with:
-        python-version: 3.8
+        python-version: "3.8"
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip