Ansible Playbook can't find pip in virtual environment

Question

I am using a basic Ansible Playbook in order to install some Python packages on a Ubuntu 18.04 system. For the sake of demonstration, take the following example playbook test.yml.

---
- name: Installing demo package.
  hosts: localhost
  tasks:
  - name: Installing with pip.
    pip:
      name:
        - "numpy"
      virtualenv: "venv"
      virtualenv_python: python3.6

I installed a virtual environment using python3 -m venv venv and activated it using source venv/bin/activate/. However, if I run ansible-playbook test.yml, I get the following error:

fatal: [localhost]: FAILED! => {"changed": false, "cmd": "venv/bin/pip install numpy", "msg": "[Errno 2] No such file or directory", "rc": 2}

Error analysis:

I ran a couple of commands from the this related question.

ansible localhost -a "which pip" returns:

localhost | SUCCESS | rc=0 >>
/home/mydir/venv/bin/pip

I tried to clear the hash using ansible localhost -m shell -a "hash -r" and obtained

localhost | SUCCESS | rc=0 >>

Afterwards, ansible localhost -m shell -a "type pip"" returns:

localhost | SUCCESS | rc=0 >>
pip is /home/mydir/venv/bin/pip

But nevertheless, the problem persists, even though I could install numpy using venv/bin/pip install numpy in a shell without any disturbances.

The version of Ansible is 2.5.1.

Answer 1

The actual path evaluated from virtualenv: "venv" might be different from what you expect. Once you have an existing virtualenv, then you can be more explicit in convincing Ansible to use it: with the executable parameter of the pip module instead of virtualenv.

---
- name: Installing demo package.
  hosts: localhost
  tasks:
  - name: Installing with pip.
    pip:
      name:
        - "numpy"
      executable: /home/mydir/venv/bin/pip