crontabberise drop_old_partitions; bug 1014128; attempt #2

This addresses bug 1014128. Again. (Previous attempt at rebasing was a horrible disaster. :unamused:) 

`?r` @peterbe and/or @rhelmer :revolving_hearts: 
Why is `eq_(result[0], 1)` preferred; or, put another way, what is wrong with `assert result[0] == 1` :question: