How can I use stdout within an ansible conditional correctly?

Question

tasks:
    - name: check if rpmforge installed
      shell: rpm -q rpmforge-release-0.5.3-1.el6.rf.i686
      register: shell_output

    - name: Enable repo for htop
      shell: "{{ item }}"
      with_items:
        - wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.i686.rpm
        - sudo rpm -Uhv rpmforge-release-0.5.3-1.el6.rf.i686.rpm
      when: shell_output.stdout.find('not installed') != -1

The above task fails with :

failed: [default] => {"changed": true, "cmd": "rpm -q rpmforge-release-0.5.3-1.el6.rf.i686", "delta": "0:00:00.100877", "end": "2016-01-08 09:05:30.495234", "rc": 1, "start": "2016-01-08 09:05:30.394357", "warnings": ["Consider using yum module rather than running rpm"]}
stdout: package rpmforge-release-0.5.3-1.el6.rf.i686 is not installed

The stdout contains the phrase 'not installed'.

Ansible version 1.9.4, running on OSX El Capitan with Vagrant & Virtualbox (latest versions as at Jan 2016)

Answer 1

Ansible sees rpm -q returning a non-zero exit code and aborts.

You'll want to change it like this to tell Ansible not to care about the exit code:

tasks:
    - name: check if rpmforge installed
      shell: rpm -q rpmforge-release-0.5.3-1.el6.rf.i686
      register: shell_output
      failed_when: false
      changed_when: false

(I also added changed_when so Ansible won't tell you something changed, like it usually does for every shell task. Because nothing changes when you query the RPM database.)

The 2nd task is fine.