Update docstring

Author: Gabriel Tincu

kafka/producer/sender.py

@@ -227,6 +227,7 @@ def _complete_batch(self, batch, error, base_offset, timestamp_ms=None, log_star
             base_offset (int): The base offset assigned to the records if successful
             timestamp_ms (int, optional): The timestamp returned by the broker for this batch
             log_start_offset (int): The start offset of the log at the time this produce response was created
+            global_error (Exception): The summarising error message
         """
         # Standardize no-error to None
         if error is Errors.NoError: