Merge pull request #28716 from rallytime/bp-28705

Back-port #28705 to 2014.7

salt/netapi/rest_tornado/saltnado.py

@@ -1577,7 +1577,12 @@ class WebhookSaltAPIHandler(SaltAPIHandler):
 
         ret = self.event.fire_event({
             'post': self.raw_data,
-            'headers': self.request.headers,
+            # In Tornado >= v4.0.3, the headers come
+            # back as an HTTPHeaders instance, which
+            # is a dictionary. We must cast this as
+            # a dictionary in order for msgpack to
+            # serialize it.
+            'headers': dict(self.request.headers),
         }, tag)
 
         self.write(self.serialize({'success': ret}))