transform: use codecs library for rot13

dr_botzo/transform/ircplugin.py

@@ -1,6 +1,7 @@
 """Assorted text transformations (e.g. rot13)."""
 
 import base64
+import codecs
 
 from ircbot.lib import Plugin
 
@@ -40,7 +41,8 @@ class Transform(Plugin):
         """Apply a rot13 method to the text."""
 
         text = match.group(1)
-        return self.bot.reply(event, text.encode('rot13', 'ignore'))
+        encoder = codecs.getencoder('rot13')
+        return self.bot.reply(event, encoder(text)[0])
 
     def handle_base64(self, connection, event, match):
         """Apply a base64 encoding to the text."""