message: Check for http errors in middleware and apply if necessary
diff: @@ -44,6 +44,8 @@ const errorRenderer = (error, request, response, next) => {/*jshint unused: fals
  error.status === 400 &&
  request.method === "POST") return applyError(response, invalidJsonError);
  + if (error instanceof PostcodesioHttpError) return applyError(response, error);
  +
  // Return 500 for all other errors
  return applyError(response, genericError);
  };
  