Rails 4 - Can't render 404 on page with dynamic error (error during failover response: no template / serving errors)

I created dynamic error pages following the instructions here: http://wearestac.com/blog/dynamic-error-pages-in-rails

They work when I navigate to them directly via / 404 or / 500, or if I try to navigate to a URL that is not handled in routes. However, when I try to force a 404 in action with render :status => 404

in production, I get the following error:

Error during failsafe response: Missing template errors/show, application/show with {:locale=>[:en, :"en-US"], :formats=>[:html, :text, :js, :css, :ics, :csv, :vcf, :png, :jpeg, :gif, :bmp, :tiff, :mpeg, :xml, :rss, :atom, :yaml, :multipart_form, :url_encoded_form, :json, :pdf, :zip], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby]}. 
Searched in:
  * "/Users/Jeremy/Projects/git/rails/app/views"

      

        
        
        
      

    

The 404 error page resides at views / errors / 404.html.erb. From the stack trace, it doesn't even look like Rails is accessing ErrorsController. (both code and trace below)

In development mode, I get the standard rails error page, which is to be expected.

application.rb

...
config.exceptions_app = self.routes
...

      

        
        
        
      

    

routes.rb

...

# Error pages
%w( 404 500 ).each do |code|
  get code, :to => "errors#show", :code => code
end

...

      

        
        
        
      

    

errors_controller.rb

class ErrorsController < ApplicationController
  def show
    render status_code.to_s, :status => status_code
  end
protected
  def status_code
    params[:code] || 500
  end
end

      

        
        
        
      

    

The stack trace doesn't seem very good:

Error during failsafe response: Missing template errors/show, application/show with {:locale=>[:en, :"en-US"], :formats=>[:html, :text, :js, :css, :ics, :csv, :vcf, :png, :jpeg, :gif, :bmp, :tiff, :mpeg, :xml, :rss, :atom, :yaml, :multipart_form, :url_encoded_form, :json, :pdf, :zip], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby]}. Searched in:
  * "/Users/Jeremy/Projects/git/rails/app/views"

  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/path_set.rb:46:in `find'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/lookup_context.rb:124:in `find'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/renderer/abstract_renderer.rb:18:in `find_template'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/renderer/template_renderer.rb:41:in `determine_template'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/renderer/template_renderer.rb:8:in `render'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/renderer/renderer.rb:42:in `render_template'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/renderer/renderer.rb:23:in `render'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/rendering.rb:99:in `_render_template'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/streaming.rb:217:in `_render_template'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionview-4.1.1/lib/action_view/rendering.rb:82:in `render_to_body'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/rendering.rb:32:in `render_to_body'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/renderers.rb:32:in `render_to_body'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/abstract_controller/rendering.rb:25:in `render'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/rendering.rb:16:in `render'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/activesupport-4.1.1/lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
  /Users/Jeremy/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/benchmark.rb:294:in `realtime'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/activesupport-4.1.1/lib/active_support/core_ext/benchmark.rb:12:in `ms'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/instrumentation.rb:41:in `block in render'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
  /Users/Jeremy/.rvm/gems/ruby-2.1.0/gems/actionpack-4.1.1/lib/action_controller/metal/instrumentation.rb:40:in `render'
  /Users/Jeremy/Projects/git/rails/app/controllers/application_controller.rb:86:in `render_not_found'
  /Users/Jeremy/Projects/git/rails/app/controllers/application_controller.rb:39:in `set_catalog_type'