Ansible – Python 2.6 support ends with Ansible 2.7

As announced with Ansible 2.7, python 2.6 will not more supported on the controller host

You can find information about this in the very usefull porting guide or in the Ansible 2.7 roadmap

Porting guides are a very interesting documentation, you will find what you have to adapt in your playbooks and roles to use an higher version of ansible.