You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: discovery.rs
    path of file: ./repos/rusoto/integration_tests/tests
    
    the code of the file until where you have to start completion: #![cfg(feature = "discovery")]

extern crate env_logger;
extern crate log;
extern crate rusoto_core;
extern crate rusoto_discovery;

use rusoto_core::{Region, RusotoError};
use rusoto_discovery::{
    DescribeTagsRequest, Discovery, DiscoveryClient, ListConfigurationsRequest,
};

use std::str;

// These tests require the calling AWS account to be whitelisted.
// See http://docs.
    
async fn should_list_configurations() {
    let _ = env_logger::try_init();

    let client = DiscoveryClient::new(Region::UsWest2);
    let request = ListConfigurationsRequest {
        configuration_type: "SERVER".to_owned(),
        ..Default::default()
    };

    match client.list_configurations(request).await {
        Ok(response) => println!("Response: {:?}", response),
        Err(e) => match e {
            RusotoError::Unknown(ref e) => {
                assert!(str::from_utf8(&e.body)
                    .unwrap()
                    .contains("is not whitelisted to access"));
            }
            _ => panic!("Error from Discovery service should be typed."),
        },
    }
}