runs-on: Ubuntu-20.04

.github/workflows/ubuntu_tests.yml

@@ -6,7 +6,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version: [2.7.18, 3.5.10, 3.6.12, 3.7.9, 3.8.7, 3.9.1]  # 2.7.6, 3.4.10, 
-    runs-on: ubuntu-latest
+    runs-on: Ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       # Normally, we would use the superbly maintained...