CI: Switch to Python 3.6

Author: aperezdc

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v1
         with:
-          python-version: 3.5
+          python-version: 3.6
       - name: Python Package Cache
         uses: actions/cache@v1
         with: