Fix location that gets used for open-ended responses

common/lib/xmodule/xmodule/capa_module.py

@@ -149,7 +149,7 @@ class CapaModule(XModule):
         # Need the problem location in openendedresponse to send out.  Adding
         # it to the system here seems like the least clunky way to get it
         # there.
-        self.system.set('location', self.location)
+        self.system.set('location', self.location.url())
 
         try:
             # TODO (vshnayder): move as much as possible of this work and error