vars_prompt not prompting

[OldhamMade]

I've tried the following config:

---
cache_dir: ~/Library/Caches/battleschool
sources:
  url:
    - name: setup.yml
      url: 'https://www.dropbox.com/s/1234567890/setup.yml?dl=1'

and setup.yml:

---
- hosts: workstation
  vars_prompt:
    - name: "some_password"
      prompt: "Enter password"
      private: yes
  tasks:
    ...

but I'm not being prompted when running battleschool as follows:
battle -XKvv --config-file=~/.battle/config.yml --become-user=$USER

[spencergibb]

Closed via 34faca3