Issue Template

Title: Upgrading yapf in tools/requirements.txt breaks the build.

Description:

Most projects are moving quickly to python/black but we can stick with yapf if we want. However, we have yapf==0.25.0 hardcoded in tools/requirements.txt and when we upgrade to the current version (0.27.0), our build fails.

• https://github.com/google/yapf/blob/master/CHANGELOG