matrix-docker-ansible-deploy/roles/matrix-bot-mjolnir/tasks/validate_config.yml

---

- name: Fail if required variables are undefined
  fail:
    msg: "The `{{ item }}` variable must be defined and have a non-null value."
  with_items:
    - "matrix_bot_mjolnir_access_token"
    - "matrix_bot_mjolnir_management_room"
  when: "vars[item] == '' or vars[item] is none"