Extract an instance id from an error

def extract_instance_id(state_error):
    "Extract an instance id from an error"
    instance_id = None
    match = RE_ERROR_INSTANCE_ID.search(str(state_error))
    if match:
        instance_id = match.groupdict().get('instance_id')
    if match is None or instance_id is None:
        raise ValueError("Could not extract instance id from error: %s" % state_error)
    return instance_id