.ansible.cfg

[defaults]
host_key_checking = False
inventory = ~/ansible_hosts.ini
library = ~/.ansible/library
display_skipped_hosts = True
nocows = 1
roles_path = ~/.ansible/roles:/etc/ansible/roles

.ansible_hosts.ini

localhost ansible_connection=local

my_playbook.yml

---

- hosts: localhost
  connection: local

  environment:
    http_proxy: http://miproxy.com:8080
    https_proxy: http://miproxy.com:8080

  tasks:

  - name: Install virtualbox key
    become: yes
    apt_key:
      url: https://www.virtualbox.org/download/oracle_vbox.asc
      state: absent

  - name: configure virtualbox repo
    become: yes
    apt_repository:
      repo: deb http://download.virtualbox.org/virtualbox/debian vivid contrib
      filename: virtualbox
      mode: 644