Use dict.popitem when we know the dict only has one key

elasticsearch/helpers.py

@@ -1,4 +1,4 @@
-from itertools import islice, chain
+from itertools import islice
 from operator import methodcaller
 try:
     from itertools import imap as map
@@ -106,7 +106,7 @@ def streaming_bulk(client, actions, chunk_size=500, raise_on_error=False, expand
         resp = client.bulk(bulk_actions, **kwargs)
 
         # go through request-reponse pairs and detect failures
-        for op_type, item in chain.from_iterable(map(methodcaller('items'), resp['items'])):
+        for op_type, item in map(methodcaller('popitem'), resp['items']):
             ok = item.get('ok')
             if not ok and raise_on_error:
                 errors.append({op_type: item})