ansible-role-tripleo-modify-image/tasks/precheck.yml

- name: Ensure that source_image is defined
  assert:
    that:
      - source_image is defined
      - source_image | length > 0

- name: Ensure that modify_dir_path is defined
  assert:
    that:
      - modify_dir_path is defined
      - modify_dir_path | length > 0