Carthage and OTP GitHub Errors

As a reminder to my self...
In Carthage if you start seeing errors "Must specify two-factor authentication OTP code"...
One way is to specify via an environment variable:
export GITHUB_ACCESS_TOKEN= <get this from Github
This comes from here: Line 145
The other option is to ensure the GitHub credential helper is working and force a credential challenge that will capture your GitHub credentials.
See this: https://help.github.com/articles/caching-your-github-password-in-git/
git credential-osxkeychain