Not emitting partition_end for a partition is incorrect. Sstable
writer assumes that it is emitted. If it's not, the sstable will not
be written correctly. The partition index entry for the last partition
will be left partially written, which will may result in errors during
reads. Also, statistics and sstable key ranges will not include the
last partition.
It's better to catch this problem at the time of writing, and not
generate bad sstables.
Another way of handling this would be to implicitly generate a
partition_end, but I don't think that we should do this. We cannot
trust the mutation stream when invariants are violated, we don't know
if this was really the last partition which was supposed to be
written. So it's safer to fail the write.
Enabled for both mc and la/ka.
43c7144133