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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def authenticate_user(token):
 """ Add the content curation Authorizatino `token` header to `config.SESSION`. """

    config.SESSION.headers.update({"Authorization": "Token {0}".format(token)})
    try:
        response = config.SESSION.post(config.authentication_url())
        response.raise_for_status()
        user = json.loads(response._content.decode("utf-8"))
        config.LOGGER.info("Logged in with username {0}".format(user['username']))
        return user['username'], token
    except HTTPError:
        config.LOGGER.error("Invalid token: Credentials not found")
        sys.exit()