Not the way to do it long term, but this will give you a chance to play with it.

From the controller node:

sudo keystone-manage fernet_setup --keystone-user keystone --keystone-group keystone
sudo crudini --set /etc/keystone/keystone.conf token provider fernet
sudo systemctl restart httpd.service

Test it

$ openstack  token issue -f shell
expires="2016-05-05T05:21:44Z"
id="gAAAAABXKspYhz7Ti5ldwi0mU4D69NqTINEU_t-e8MoxqVkVhR40w1E7GOmgai-9lanr2Z6bnoyQSgNWIhD63UOm1Mlsm9_hw5oTCqVO_pWJZwTomlWM2BrG5LqTOyp6PNqYz2pZ0DIaSTOnOQPeVqKp4ot8S3B6oA4Xy1JZo3305DPiApCzOyQ"
project_id="b383d314cc344639939f2a9a381a6945"
user_id="4e154e7d166d4bd6b8199dfd3a6f2468"