Don't issue raw rollback

[0x0badc0de]

PR #809 includes a code which issues raw rollback into a database rolling back all the changes made before calling this code. There was very valid comment regarding this #809 (comment)
Can this code be refactored at least to use nested transaction, raise ActiveRecord::Rollback (or another one) or even rethrow original exception probably configured w/ some option. It would be much better to have an exception in caller code rather than all the changes silently discarded by raw rollback.