To set up your environment for developing on Custom Runtime:
Install and initialize the gcloud CLI for deploying and managing
your apps. If you already
have the gcloud CLI installed and initialized, run the
gcloud components update
command to update to the latest release.
By downloading, you agree to be bound by the Terms that
govern use of the gcloud CLI for App Engine.
To locally test and run your App Engine custom runtime apps,
install Docker: