Rails 2.3-style plugins and deprecation warnings running task in Heroku

Are you using Heroku?

Heroku will inject plugins in Rails 3.x applications .. To avoid this injection in Rails 3, include the rails_12factor gem in your application. (Heroku Ruby Support 2013-10-26)

The rails_12factor gem is also required in rails 4.

If this gem is not present in your application, you will receive a warning while deploying, and your assets and logs will not be functional. (Rails 4 on Heroku 2013-10-26)

As recently as 2013-08, heroku always injected plugins in rails 3 apps, even apps with the recommended gems. This was an issue with the ruby buildpack, and was fixed by PR 11, merged on 2013-08-06.

You can try

::ActiveSupport::Deprecation.silenced = true

in your production.rb since it's just noise.