REST Server error (unable to locate class session.php)

I setup the RestServer from https://github.com/chriskacerguis/codeig...restserver

Trying to run the api example on my server. Using CI 3.0

Copied the example.php to the directory  /application/controllers/api

Using postman, issued a GET to servername/api/example

I am getting the error Unable to locate the specified class: Session.php. and HTTP Code 503 Service Unavailable 

This looks like a configuration error to me

I have not made any changes to example.php 

Any ideas?