```ruby
module Outpost
  module Controller
    module CustomErrors
      extend ActiveSupport::Concern
      
      included do
        rescue_from StandardError, with: ->(e) { render_error(500, e) }
        
        rescue_from ActionController::RoutingError, ActionView::MissingTemplate, 
          ActionController::UnknownController, ::AbstractController::ActionNotFound, 
          ActiveRecord::RecordNotFound, with: ->(e) { render_error(404, e) }
      end
      
      #----------------------
      
      def render_error(status, e=StandardError)
        if Rails.application.config.consider_all_requests_local
          raise e
        else
          render template: "errors/error_#{status}", status: status, locals: { error: e }
        end
      end
    end # CustomErrors
  end
end
```

Support Rails 4 UnknownFormat in CustomErrors
user
```ruby
module Outpost
  module Controller
    module CustomErrors
      extend ActiveSupport::Concern
      
      NOT_FOUND_ERROR_CLASSES = [
        ActionController::RoutingError, 
        ActionView::MissingTemplate, 
        ActionController::UnknownController, 
        AbstractController::ActionNotFound, 
        ActiveRecord::RecordNotFound
      ]

      if defined?(ActionController::UnknownFormat)
        NOT_FOUND_ERROR_CLASSES << ActionController::UnknownFormat
      end

      included do
        rescue_from StandardError, with: ->(e) { render_error(500, e) }
        rescue_from *NOT_FOUND_ERROR_CLASSES, with: ->(e) { render_error(404, e) }
      end
      
      #----------------------
      
      def render_error(status, e=StandardError)
        if Rails.application.config.consider_all_requests_local
          raise e
        else
          render template: "errors/error_#{status}", status: status, locals: { error: e }
        end
      end
    end # CustomErrors
  end
end
```
assistant