List admin API keys.

def keys():
    """List admin API keys."""
    for admin in current_app.config['ADMIN_USERS']:
        try:
            db.get_db()  # init db on global app context
            keys = ApiKey.find_by_user(admin)
        except Exception as e:
            click.echo('ERROR: {}'.format(e))
        else:
            for key in keys:
                click.echo('{:40} {}'.format(key.key, key.user))