message: test(registry): Allow `custom_responders` to call normal responders
diff: @@ -5,6 +5,7 @@ use cargo_test_support::paths;
  use cargo_test_support::registry::{self, Package, Response};
  use cargo_test_support::{basic_manifest, no_such_file_err_msg, project, publish};
  use std::fs;
  +use std::sync::{Arc, Mutex};
  const CLEAN_FOO_JSON: &str = r#"
  {
  