On Python 3 we need to make sure bytes get written to the websocket.

src/allmydata/web/logs.py

@@ -5,6 +5,8 @@ from __future__ import (
     division,
 )
 
+from future.builtins import str
+
 import json
 
 from autobahn.twisted.resource import WebSocketResource
@@ -49,7 +51,11 @@ class TokenAuthenticatedWebSocketServerProtocol(WebSocketServerProtocol):
         """
         # probably want a try/except around here? what do we do if
         # transmission fails or anything else bad happens?
-        self.sendMessage(json.dumps(message))
+        encoded = json.dumps(message)
+        if isinstance(encoded, str):
+            # On Python 3 dumps() returns Unicode...
+            encoded = encoded.encode("utf-8")
+        self.sendMessage(encoded)
 
     def onOpen(self):
         """