We have a requirement where in only one producer should be writing to a partition at once.
 For this we had to write our own producer (which will be open sourced soon).
 And also create this patch to validate the offsets which are sent by the producer.
 This validation is put because we are running many producers in leader/follower mode using zookeeper leader election algorithm.
 We'd like to prevent a situation in which a follower thinks that he's a leader and tries to produce a message. This phantom producer is expected to receive this new ProduceOffset error and will handle it appropriately.