ansible failed_when

#### Running the task without condition shows us the 'stdout' msg

TASK [qualitybox : Pear | install pear mail module] ****************************
ok: [wiki.example.com] => {
    "changed": false,
    "invocation": {
        "module_args": {
            "name": "Mail",
            "state": "latest"
        },
        "module_name": "pear"
    },
    "msg": "package(s) already installed"
}

TASK [qualitybox : debug] ******************************************************
task path: /home/greg/src/ansible-digitalocean/roles/qualitybox/tasks/install_pear.yml:71
ok: [wiki.example.com] => {
    "msg": {
        "changed": false,
        "msg": "package(s) already installed"
    }
}

#### So we try to incorporate a 'changed_when' and 'failed_when' condition

- name: Pear | install pear mail module
  pear: name=Mail state=latest
  register: pear_result
  changed_when: "'already installed' not in pear_result.stdout"
  failed_when: "'already installed' not in pear_result.stdout and pear_result.stderr"

###### But we get an error

fatal: [wiki.example.com]: FAILED! => {
    "failed": true,
    "msg": "The conditional check ''already installed' not in pear_result.stdout' failed. The error was: error while evaluating conditional ('already installed' not in pear_result.stdout): Unable to look up a name or access an attribute in template string ({% if 'already installed' not in pear_result.stdout %} True {% else %} False {% endif %}).\nMake sure your variable name does not contain invalid characters like '-': argument of type 'StrictUndefined' is not iterable"
}


###### SOLVED: The reason this fails is because the ansible extras PEAR module does NOT return 'stdout'.  Instead there is the 'msg' attribute which we can test:
###### SEE https://github.com/ansible/ansible-modules-extras/blob/devel/packaging/language/pear.py

  changed_when: "'already installed' not in pear_result.msg"