Add a role that can be used to ensure required variables exist before running a role's tasks. To use:
Add a role that can be used to ensure required variables exist before
running a role's tasks. To use:

1. Create <role>/meta/required_vars.yml, which should contain (at the top
   level) a list of variable names.
2. Add this role to the top of your play like so:
    roles:
      - name: required_vars
        required_vars_roles: <role name or role name list>
        tags: always

galaxyproject/ansible-common-roles,galaxyproject/ansible-common-roles