Test older Pillow versions

.github/workflows/python-tests.yml

@@ -1,6 +1,15 @@
 name: Run unit tests
 
 on: [push, pull_request]
+# on:
+#   pull_request:
+#   push:
+#     branches:
+#     - master
+#     tags:
+#   schedule:
+#     # Run everyday at 03:53 UTC
+#     - cron: 53 3 * * *
 
 jobs:
   build:
@@ -8,6 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
+        fail-fast: false
         python-version: [3.6, 3.7, 3.8, pypy3]
 
     steps:
@@ -21,9 +31,10 @@ jobs:
         sudo apt install ffmpeg
         ffmpeg -version
     - name: Install Tox
-      run: pip install tox
+      run: python -m pip install tox tox-gh-actions
     - name: Run Tox
-      # Run tox using the version of Python in `PATH`
-      run: tox -e py
+      run: tox
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v1
+      with:
+        file: ./coverage.xml