Delete an RDS parameter group.

    CLI example::

        salt myminion boto_rds.delete_parameter_group my-param-group \
                region=us-east-1

def delete_parameter_group(name, region=None, key=None, keyid=None,
                           profile=None):
    '''
    Delete an RDS parameter group.

    CLI example::

        salt myminion boto_rds.delete_parameter_group my-param-group \
                region=us-east-1
    '''
    try:
        conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)
        if not conn:
            return {'results': bool(conn)}

        r = conn.delete_db_parameter_group(DBParameterGroupName=name)
        return {'deleted': bool(r), 'message':
                'Deleted RDS parameter group {0}.'.format(name)}
    except ClientError as e:
        return {'error': __utils__['boto3.get_error'](e)}