Fix error var name in _unpack (#1403)
Fix error var name in _unpack (#1403)

Change-Id: I6527da4b70ebec9e08fa50aca9eba717b8361f19
mumrah/kafka-python,wikimedia/operations-debs-python-kafka,Yelp/kafka-python,ohmu/kafka-python,scrapinghub/kafka-python,ohmu/kafka-python,scrapinghub/kafka-python,Aloomaio/kafka-python,wikimedia/operations-debs-python-kafka,DataDog/kafka-python,mumrah/kafka-python,Yelp/kafka-python,dpkp/kafka-python,dpkp/kafka-python,Aloomaio/kafka-python