Fix failing builds due to new docker-py release.

Author: geerlingguy

tests/docker.yml

@@ -3,7 +3,9 @@
 
  vars:
  pip_install_packages:
- - docker
+ # See: https://github.com/ansible/ansible/issues/35612
+ - name: docker
+ version: "2.7.0"
 
  pre_tasks:
  - name: Update the apt cache so we can install ufw.