It seems that cloudlet_manager.py wasn't installed and so nova cannot find it. In the openstack-ext.yml file, there is a task to copy cloudlet_manager.py to /usr/lib:
shell: "cp ~/elijah-openstack/compute/cloudlet_manager.py /usr/lib/python2.7/dist-packages/nova/compute/cloudlet_manager.py"
If you still have the output from the ansible-playbook command, check to see if there were any failures. You can also check /usr/lib/python2.7/dist-packages/nova/compute for the file. I am assuming you used the default configuration where the controller and the compute for OpenStack are on the same node, but if not, you will have to check on the compute node(s).
You can also try to repair the installation by re-running the ansible playbook with the --tags option. This will allow you to specify just the compute tasks and skip the rest of the installation steps. You can either supply 'compute' which will run all of the compute related tasks or 'openstack-compute-ext' which will just perform the steps to install the OpenStack extension pieces (which includes the copying of cloudlet_manager.py). For instance:
ansible-playbook -i ./hosts openstackpp.yml --tags openstack-compute-ext