return -2 if last_offset_consumed is -1. fixes #216
return -2 if last_offset_consumed is -1. fixes #216

wikimedia/operations-debs-python-pykafka,thedrow/samsa,thedrow/samsa,benauthor/pykafka,wikimedia/operations-debs-python-pykafka,thedrow/samsa,wikimedia/operations-debs-python-pykafka,benauthor/pykafka,benauthor/pykafka