Fix python proxy to not crash when fed unicode data in getstate and setstate.

doc/bugs/proxy.py_utf8_troubles.mdwn

@@ -31,3 +31,5 @@ python3 and we'd just move the problem to the stderr writing later on; instead,
 debug output doesn't look that pretty any more, but is safe.
 
 --[[chrysn]]
+
+> ok, [[done]] --[[Joey]] 

plugins/proxy.py

@@ -175,7 +175,7 @@ class _IkiWikiExtPluginXMLRPCHandler(object):
         data = _xmlrpc_client.loads(xml)[0][0]
         self._debug_fn(
             'parsed data from response to procedure {0}: [{1}]'.format(
-                cmd, data))
+                cmd, repr(data)))
         return data
 
     def handle_rpc(self, in_fd, out_fd):