Use a list to store feed data in JSONUnmarshaller

Creating a new string could be very expensive for large amount of data,
especially because xmlrpclib read response and feed the parser with chunk of
1024. So it is better to store the feed data in a list and create the string
only once when closing the parser.

issue5237
review19951003

tryton/jsonrpc.py

@@ -125,13 +125,14 @@ class JSONParser(object):
 
 
 class JSONUnmarshaller(object):
-    data = ''
+    def __init__(self):
+        self.data = []
 
     def feed(self, data):
-        self.data += data
+        self.data.append(data)
 
     def close(self):
-        return json.loads(self.data, object_hook=object_hook)
+        return json.loads(''.join(self.data), object_hook=object_hook)
 
 
 class Transport(xmlrpclib.Transport, xmlrpclib.SafeTransport):