[SOLVED] requests returning HTTP 404 when I follow a link after I do a POST

[JChris]

I get one free ebook a day from Packt Publishing with their "Free Learning - Free Technology Ebooks" promo. I'm trying to automate this process. I do a POST against their root path to login, after that I do a GET on the promo URL and use BeautifulSoup 4 to get the HREF of the "claim your free ebook" link, and now I'm stuck. Here's the code:

    #!/usr/bin/env python
    # -*- coding: utf-8 -*-
    
    import requests
    from bs4 import BeautifulSoup
    
    USERNAME = '[email protected]'
    PASSWORD = 'secret'
    BASE_URL = 'https://www.packtpub.com'
    PROMO_URL = 'https://www.packtpub.com/packt/offers/free-learning'
    
    session = requests.session()
    headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2810.1 Safari/537.36'}
    session.post(BASE_URL, {"username": USERNAME, "password": PASSWORD}, headers=headers)
    
    response = session.get(PROMO_URL, headers=headers)
    soup = BeautifulSoup(response.text, 'html.parser')
    current_offer_href = BASE_URL + soup.find("div", {"class": "free-ebook"}).a['href']
    print(current_offer_href)
    print(session.get(current_offer_href, headers=headers))

The current_offer_href is holding the correct value, if you go to the site today (13/NOV/2016) and inspect the button you will find it. In this case, it's holding https://www.packtpub.com/freelearning-claim/17276/21478. If I try to do a GET against current_offer_href I receive <Response [404]>. In reality what I should be getting is a redirect to https://www.packtpub.com/account/my-ebooks, because that's what happen if I click the button manually on the site. What's wrong here?