Update python-app.yml

Author: claucece

.github/workflows/python-app.yml

@@ -26,6 +26,7 @@ jobs:
     - name: Install dependencies
       run: |
         sudo apt-get update
+        apt-cache policy sagemath
         python -m pip install --upgrade pip
         pip install flake8 pytest
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi