Refer to the exhibit.

Refer to the exhibit. A user makes a request to authenticate and retrieve a token to consume resources. The user encodes the username and password in base64 format and makes a POST request to the server. The server responds with a 401 Unauthorized status and provides the information to allow authorization by using a WWW-Authenticate response header. Which code snippet must be placed in the blank in the code to complete the Python script that retrieves the resource?