Add QE setup tool support for BitTorrent downloads

Fixes #1871

util/registry/torrent.py

@@ -21,7 +21,10 @@ def _load_private_key(private_key_file_path):
   with open(private_key_file_path) as private_key_file:
     return private_key_file.read()
 
-def _torrent_jwt(info_dict):
+def torrent_jwt(info_dict):
+  """ Returns an encoded JWT for the given information dictionary, signed by the local instance's
+      private key.
+  """
   token_data = {
     'iss': instance_keys.service_name,
     'aud': ANNOUNCE_URL,
@@ -45,7 +48,7 @@ def make_torrent(name, webseed, length, piece_length, pieces):
   }
 
   return bencode.bencode({
-    'announce': ANNOUNCE_URL + "?jwt=" + _torrent_jwt(info_dict),
+    'announce': ANNOUNCE_URL + "?jwt=" + torrent_jwt(info_dict),
     'url-list': webseed,
     'encoding': 'UTF-8',
     'created by': REGISTRY_TITLE,