Fixing error return to be consistent with tuple return at the end of the method.

diff --git a/requests/models.py b/requests/models.py
index 2439153371346f7706b075d8f72370a79de78d84..9289f3ba2609a46f841136f5dca2ce2ed664d4e8 100644 (file)
--- a/requests/models.py
+++ b/requests/models.py
@@ -93,7 +93,7 @@ class RequestEncodingMixin(object):
 
         """
         if (not files) or isinstance(data, str):
-            return None
+            return (None, None)
 
         new_fields = []
         fields = to_key_val_list(data or {})