message: CircleCI: Upgrade build-image to Python 3
diff: @@ -124,7 +124,7 @@ jobs:
  - run: ci/do_circle_ci.sh check_spelling
  build_image:
  docker:
  - - image: circleci/python:2.7
  + - image: circleci/python:3.7
  environment:
  # See comment in do_circle_ci.sh for why we do this.
  NUM_CPUS: 8
  