We use a git Pre-Push hook .git/hooks/pre-push. Unsurprisingly, it's run right before pushing code to the repo. That hook does things like runs our test suite and Flake8 lint checks.
If any of the tests or the flake8 process fail, the script exits with a non-zero status and this prevents the git push from going through. Fix your code, commit, and try again.
If you want to force a push, of untested, unlinted code, use the flag like:
git push --no-verify
and hang your head shame in.
I've created a build-badge for the top README.rst. On the
CircleCI's projects page hit Settings for this project then Status
Badges. Since this is a private repo, I had to crate a new token,
which I called scaffold-serverless-build-badge, then selected
reStructuredText and pasted the generated code in the README file.