Ran into this one at work today.
Ugpraded delayed_job gem from 3.0.3 to 3.0.4 and started getting the following error when trying to queue up jobs
Delayed::Job.enqueue(MyJob.new()) # BARF ActiveRecord::UnknownAttributeError (unknown attribute: queue)
Someone upgraded us to 3.0.0 and missed the post install instructions of running
rails generate delayed_job:upgrade which adds the queue coloumn to the delayed tasks table. There is a ticket here if you want more info.
Hope this comes up on google for upgrading 3.0.3 to 3.0.4 and saves you guys a few minutes.