Fix link filtering

Author: dstansby

check-links.py

@@ -12,7 +12,7 @@
 
 broken_links = [(ref.ref, code) for ref, code in zip(refs, status_codes) if code != 200]
 # It seems that Twitter and stackoverflow do not respond well to the link checker and throws a 400
-broken_links = [b for b in broken_links if not ('twitter.com' in b or 'stackoverflow.com' in b)]
+broken_links = [b for b in broken_links if not ('twitter.com' in b[0] or 'stackoverflow.com' in b[0])]
 
 if len(broken_links) == 0:
     sys.exit(0)