23:54:48 ** Execute plugin:assets:precompile
23:54:48 rake aborted!
23:54:48 NoMethodError: undefined method `register_engine' for nil:NilClass
23:54:48 /usr/share/foreman/lib/tasks/plugin_assets.rake:52:in `initialize'
23:54:48 /usr/share/foreman/lib/tasks/plugin_assets.rake:107:in `new'
23:54:48 /usr/share/foreman/lib/tasks/plugin_assets.rake:107:in `block in <top (required)>'
23:54:48 /usr/share/foreman/vendor/ruby/2.1.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `call'

Related: https://github.com/rails/sprockets-rails/issues/237

This is breaking all new packaging of plugins for DEB.