diff -r b1834143fec8 -r eabacd3c6f16 web/application.py
--- a/web/application.py	Mon Oct 05 17:57:03 2015 +0200
+++ b/web/application.py	Tue Oct 06 11:07:22 2015 +0200
@@ -500,7 +500,7 @@
             # don't overwrite it if it's already set
             req.status_out = status
         json_dumper = getattr(ex, 'dumps', lambda : json.dumps({'reason': text_type(ex)}))
-        return json_dumper()
+        return json_dumper().encode('utf-8')
 
     # special case handling