programmatically (with `new Response.Builder()`) you must now always supply
    a message. An empty string `""` is permitted. This value was never null on
    responses returned by OkHttp itself, and it was an old mistake to permit
    application code to omit a message.

 *  The challenge's scheme and realm are now non-null. If you are calling
    `new Challenge(scheme, realm)` you must provide non-null values. These were