message: Add support for local s3 endpoint
  Fallback is always AWS, but this allows easy use of minio and the like
  for local development.
diff: @@ -96,7 +96,10 @@ fn s3_client() -> S3Client {
  let client = S3Client::new_with(
  rusoto_core::request::HttpClient::new().unwrap(),
  EnvironmentProvider::default(),
  - Region::UsWest1,
  + std::env::var("S3_ENDPOINT").ok().map(|e| Region::Custom {
  + name: "us-west-1".to_owned(),
  + endpoint: e,
  + }).unwrap_or(Region::UsWest1),
  );
  client
  }
  