Ansible issue https://github.com/ansible/ansible/issues/17078

ansible-playbook test-nok.yml -v

No config file found; using defaults
 [WARNING]: Host file not found: /etc/ansible/hosts

 [WARNING]: provided hosts list is empty, only localhost is available


PLAY [localhost] ***************************************************************

TASK [joeri : uri] *************************************************************
ok: [localhost] => {"accept_ranges": "none", "cache_control": "private, max-age=0", "changed": false, "connection": "close", "content_type": "text/html; charset=ISO-8859-1", "date": "Sat, 13 Aug 2016 15:23:03 GMT", "expires": "-1", "msg": "OK (unknown bytes)", "p3p": "CP=\"This is not a P3P policy! See https://www.google.com/support/accounts/answer/151657?hl=en for more info.\"", "redirected": true, "server": "gws", "set_cookie": "NID=84=XC_MAdNNNJKtqfn6qksIr-Fic-41ncLm4viwp-j_ufdMsn0nqFJ2cnbiBx_sgla2UMRDJg9p1PbjBR4ogLoU9OyQmlhubTy0Zzp8sjTNzQRhyjv2GjK-rbarpmWJqaxK; expires=Sun, 12-Feb-2017 15:23:03 GMT; path=/; domain=.google.be; HttpOnly", "status": 200, "url": "http://www.google.be/?gfe_rd=cr&ei=VzuvV8CRA4HEaJXam1g", "vary": "Accept-Encoding", "x_frame_options": "SAMEORIGIN", "x_xss_protection": "1; mode=block"}

PLAY RECAP *********************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0   

ansible-playbook test-ok.yml -v

No config file found; using defaults
 [WARNING]: Host file not found: /etc/ansible/hosts

 [WARNING]: provided hosts list is empty, only localhost is available


PLAY [localhost] ***************************************************************

TASK [joeri : uri] *************************************************************
ok: [localhost] => {"changed": false, "failed": false, "msg": "custom module run"}

PLAY RECAP *********************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0   

joeri - library - uri.py

#! /usr/bin/python

print '{"changed": false, "failed": false, "msg": "custom module run"}'

joeri - tasks - main.yml

- uri: url=http://google.com

test-nok.yml

---
- hosts: nonexistent
  tasks:
  - name:
    debug:

- hosts: localhost
  gather_facts: false
  roles:
    - role: joeri

test-ok.yml

---
- hosts: nonexistent
  tasks:
  - debug:

- hosts: localhost
  gather_facts: false
  roles:
    - role: joeri

tree view of files

.
├── joeri
│   ├── library
│   │   └── uri.py
│   └── tasks
│       └── main.yml
├── test-nok.yml
└── test-ok.yml