BeautifulSoup's find method returning None instead of a link

Thanks for looking into my issue here, I am trying to get the next page link from an old Reddit blog page but somehow find method is returning me None object, the code :

 def crawl(self):
        curr_page_url = self.start_url
        curr_page = requests.get(curr_page_url)
        bs = BeautifulSoup(curr_page.text,'lxml')
        # all_links = GetAllLinks(self.start_url)
        nxtlink = bs.find('a',attrs={'rel':'nofollow next'})['href']
        print(nxtlink)

and the HTML page link is Old Reddit page link on this page I'm trying to get the next pages' link is in a span tag this one :

<span class="next-button">
    <a href="https://old.reddit.com/r/learnprogramming/?count=25&amp;after=t3_j54ae2" rel="nofollow 
    next">next ›
    </a>
</span>