Read about it in the blog post.
The script has been udpated since publishing the blog post. It now supports more recent versions of python-novalcient. In addtion to the description in the blog post, the updated version of the script requires the environment variable OS_COMPUTE_API_VERSION to be set to either 1.1, 2, or 3 according to your OpenStack installation, e.g., OS_COMPUTE_API_VERSION=1.1.