test: ci should cancel older jobs

Author: nedbat

.github/workflows/tests.yml

@@ -12,11 +12,18 @@ on:
     # week, Sundays at 6:00 UTC.
     - cron: "0 6 * * 0"
 
+concurrency:
+  group: "${{ github.workflow }}-${{ github.ref }}"
+  cancel-in-progress: true
 
 defaults:
   run:
     shell: bash
 
+env:
+  PIP_DISABLE_PIP_VERSION_CHECK: 1
+  FORCE_COLOR: 1    # Get colored pytest output
+
 jobs:
   tests:
     name: "Python ${{ matrix.python-version }} on ${{ matrix.os }}"