solution

fail_when.yml

@@ -1,30 +0,0 @@
----
-- hosts: centos
-  tasks:
-
-  - name: print a message
-    debug:
-      msg: "OS on {{ inventory_hostname }} is {{ ansible_distribution }}"
-
-  - name: send script
-    copy:
-      src: "{{ item }}"
-      dest: /tmp/
-      mode: 0750
-    loop:
-    - random.sh
-    - bad.sh
-
-  - name: execute bad script
-    command: "/tmp/bad/sh"
-    ignore_errors: true
-
-  - name: execute random script
-    command: /tmp//random.sh
-    register: result
-    failed_when: 2|string in result.stdout
-
-  - name: display result
-    debug:
-      var: result
-    when: 1|string in result.stdout