EDUCATOR-139 add log to identify the cause of error

common/lib/xmodule/xmodule/x_module.py

@@ -881,7 +881,21 @@ class XModule(HTMLSnippet, XModuleMixin):
                 request_post[key] = map(FileObjForWebobFiles, request.POST.getall(key))
 
         response_data = self.handle_ajax(suffix, request_post)
-        return Response(response_data, content_type='application/json')
+
+        try:
+            return Response(response_data, content_type='application/json')
+        except TypeError:
+            request_environ = getattr(request, 'environ')
+            log.exception(
+                'Response creation failed for problem url: %s, response_data type: %s, LANG: %s, '
+                'LC_ALL: %s and HTTP_ACCEPT_ENCODING: %s',
+                request_environ.get('HTTP_REFERER'),
+                type(response_data),
+                request_environ.get('LANG'),
+                request_environ.get('LC_ALL'),
+                request_environ.get('HTTP_ACCEPT_ENCODING')
+            )
+            raise
 
     def get_child(self, usage_id):
         if usage_id in self._child_cache: