I would personally use Requests and BeautifulSoup (both modules are included by default with Pythonista).

Furthermore, I would set up the HTTP request to use a modified User-Agent value, in order to hide that you're running this from a script, and pose as a regular web browser (note that this is not foolproof, but it helps).

If you only need the links to the CSS, you can instruct BeautifulSoup to parse only to links, thus speeding up the process, by using the SoupStrainer class (more info here).

Hope this helps.