ActiveRecord::yaml_new raises DeserializationError if object not found 

This silently overrides yaml standard logic thus breaks existing functionality (it is not required by yaml to have a persistent ar object to be able to load it from yaml representation by default and this should not be changed by a gem).

This is basically the same request with this one: https://github.com/collectiveidea/delayed_job/pull/282 but a bit refactored. The pull request was closed but not implemented previously. So the BUG is still present in the master branch.