The new parameter to urlopen is "context" not "ctx"

register_new_matrix_user

@@ -52,7 +52,7 @@ def request_registration(user, password, server_location, shared_secret):
         if sys.version_info[:3] >= (2, 7, 9):
             # As of version 2.7.9, urllib2 now checks SSL certs
             import ssl
-            f = urllib2.urlopen(req, ctx=ssl.SSLContext(ssl.PROTOCOL_SSLv23))
+            f = urllib2.urlopen(req, context=ssl.SSLContext(ssl.PROTOCOL_SSLv23))
         else:
             f = urllib2.urlopen(req)
         f.read()