Fix ObjectDoesNotExist exception recovering pages with Reversion (reloaded)

[lewiscollard]

This was previously done in #175. I prefer this implementation because:

1. It fixes it in one place, not two
2. It's addressing the problem, which is Watson throwing an exception on .content, in a narrower scope
3. It doesn't quietly swallow ObjectDoesNotExist, which is something that we absolutely do want to be thrown if it happens.