List admin users.

def users():
    """List admin users."""
    for admin in current_app.config['ADMIN_USERS']:
        try:
            db.get_db()  # init db on global app context
            user = User.find_by_username(admin)
        except Exception as e:
            click.echo('ERROR: {}'.format(e))
        else:
            if user:
                click.echo('{} {}'.format(user.id, user.name))