Setting python virtualenv prompt?

[Roy Smith]

I've got the pip module working to set up my virtualenv:

  tasks:
  - name: create virtualenv and install third-party packages
    pip: chdir="{{ remote_base_dir }}/deploy"
         virtualenv=python-env
         executable="{{ remote_base_dir }}/deploy/python-env/bin/pip"
         requirements={{ item }}
    with_items:
      - base-requirements
      - web-requirements

But, I'd like to also customize the python prompt by passing:

--prompt="(my prompt) "

to the virtualenv command.  How can I do that?