Define dependencies

.github/workflows/python-app.yml

@@ -16,12 +16,13 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
-    - name: Set up Python 3.10
+    - name: Set up Python 3.8
       uses: actions/setup-python@v3
       with:
-        python-version: "3.10"
+        python-version: "3.8"
     - name: Install dependencies
       run: |
+        sudo apt install python3.8-tk
         python -m pip install --upgrade pip
         pip install flake8 pytest
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi

requirements.txt

@@ -0,0 +1 @@
+Pillow~=8.1.2