---
- name: Check if ansible is already nopasswd in sudoers
  lineinfile:
    state: absent
    path: /etc/sudoers
    regexp: "^ansible"
  check_mode: true
  changed_when: false
  register: checkallowusers

- name: Define ansible nopasswd in sudoers
  lineinfile:
    state: present
    path: /etc/sudoers
    line: "ansible ALL=(ALL:ALL) NOPASSWD"
  when: checkallowusers.found == 0
...