Ansible doesn't see an installed Python module

Question

I am trying to create an Ansible playbook which would setup a local Postgres database to be used for local/dev testing of a certain app.

postgresql_db

Answer 1

This is caused by a well-known and described behaviour of Ansible.

---

In short, if you specify localhost wherever in your inventory, Ansible will default to using /usr/bin/python for running the modules regardless of the connection: local setting.

This in turn will cause problems if additional libraries were installed in a Python environment used to execute a playbook, but not for the /usr/bin/python.

The solution is to specify ansible_python_interpreter for the localhost. In your case:

[my_ws]
localhost ansible_python_interpreter={{ansible_playbook_python}}

---

Because of the above, the test to verify module presence should be:

- command: "{{ ansible_python_interpreter | default('/usr/bin/python') }} -c 'import {{ module }}; print({{ module }}.__version__)'"
  vars:
    module: psycopg2
  register: test
- debug:
    var: test.stdout