Fix a potential bug where an OR ID might have been unprocessed base64.

 * CHANGE bridgedb.parse.networkstatus.parseRLine() to check the OR
   nickname validity only after parsing (and readding the base64 padding
   to) the OR ID digest.
 * ADD inline comments about why this is done.

lib/bridgedb/parse/networkstatus.py

@@ -103,18 +103,25 @@ def parseRLine(line):
                 "Wrong number of fields in networkstatus 'r'-line: %r" % line)
 
         nickname, ID = fields[:2]
-        isValidRouterNickname(nickname)
 
         try:
             ID = parseUnpaddedBase64(ID)
         except InvalidBase64 as error:
             raise InvalidNetworkstatusRouterIdentity(error)
 
+        # Check the nickname validity after parsing the ID, otherwise, if the
+        # nickname is invalid, we end up with the nickname being ``None`` and
+        # the ID being unparsed, unpadded (meaning it is technically invalid)
+        # base64.
+        isValidRouterNickname(nickname)
+
     except NetworkstatusParsingError as error:
         logging.error(error)
         nickname, ID = None, None
     except InvalidRouterNickname as error:
         logging.error(error)
+        # Assume that we mostly care about obtaining the OR's ID, then it
+        # should be okay to set the nickname to ``None``, if it was invalid.
         nickname = None
     except InvalidNetworkstatusRouterIdentity as error:
         logging.error(error)