in src/aws/builder.rs [1581:1591]
fn aws_test_client_opts() {
let key = "AWS_PROXY_URL";
if let Ok(config_key) = key.to_ascii_lowercase().parse() {
assert_eq!(
AmazonS3ConfigKey::Client(ClientConfigKey::ProxyUrl),
config_key
);
} else {
panic!("{} not propagated as ClientConfigKey", key);
}
}