Getting started with Ansible

I've read information elsewhere suggesting that Ansible is usable with bigip versions 11.6 or 12.x. I've got a mix of 11.4.1 and 11.5.4. Am i out of luck? Initial attempts are generating the following message:

PLAY [F5s] ****************************************************************************************************************************

TASK [create shared directory] ******************************************************************************************************** fatal: [ltm_name]: FAILED! => {"changed": false, "failed": true, "msg": "Error: ansible requires the stdlib json or simplejson module, neither was found!"}

For now I'm just trying to do standard unix admin stuff, setting up a configuration backup job that runs from cron.