Add a check that dev_path is valid

[Wtower]

Because of the fact that a project may be deployed by any dev machine, and the dev_path may differ and eventually lead to a mess up, add a check that it is a valid path on local.

Use:

- name: ...
  local_action: stat path={{ dev_path }}/index.wsgi
  register: X
  fail_when: X.stat.exists == False

Relevant links:

• http://docs.ansible.com/ansible/playbooks_delegation.html
• https://raymii.org/s/tutorials/Ansible_-_Only_if_a_file_exists_or_does_not_exist.html
• http://stackoverflow.com/questions/28855236/copy-local-file-if-exists-using-ansible