title: ActiveRecord rollback and return RecordInvalid message
body: <p>I want to save multiple objects, and rollback all if any of them fail. But I also want to render the ActiveRecord::RecordInvalid message so the user knows why it didn't save. How do I do this?</p>
  
  <pre><code>def save_multiple_things_or_error
    ActiveRecord::Base.transaction do
      thing_one.save!
      thing_two.save!
    rescue ActiveRecord::RecordInvalid =&gt; exception
      # exception.message is what I want to render
      raise ActiveRecord::Rollback
    end
  end
  </code></pre>
  
  <p>This doesn't work for a few reasons. I believe the rescue should be in a begin end block, but then if I raise the rollback, I lose the RecordInvalid exception.</p>