Retrying github actions

.github/workflows/tests.yml

@@ -4,17 +4,21 @@ on: [push, pull_request]
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [2.7, 3.4, 3.5, 3.6, 3.7, 3.8]
+
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Download submodules
         run: |
           git submodule update --init --recursive
           git submodule sync -q
           git submodule update --init
-      - name: Set up Python
+      - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v1
         with:
-          python-version: [2.7, 3.4, 3.5, 3.6, 3.7, 3.8]
+          python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip