Fix rendering of error pages to remove deprecation warning for rails 6.0

app/views/errors/error_404.haml

@@ -1,10 +1,5 @@
 - content_for(:page_title) do
   The page you were looking for doesn't exist (404)
 
-.transparent.big-number
-  404
 %h3
   These are not the kittens you're looking for. Move along.
-%p
-  %a{href: "javascript:history.back()"}
-    Go Back?

app/views/errors/error_422.haml

@@ -1,13 +1,7 @@
 - content_for(:page_title) do
   The change you wanted was rejected (422)
 
-.transparent.big-number
-  422
 %h3
   The change you wanted was rejected.
 %p
   Maybe you tried to change something you didn't have access to.
-
-%p
-  %a{href: "javascript:history.back()"}
-    Go Back?

app/views/errors/error_500.haml

@@ -1,8 +1,6 @@
 - content_for(:page_title) do
   We're sorry, but something went wrong (500)
 
-.transparent.big-number
-  500
 %h3
   Internal server error.
   Our bad! Sorry about that. :(
@@ -10,7 +8,3 @@
 - if AppConfig.admins.podmin_email?
   %p
     Drop us an email to <a href="mailto:#{AppConfig.admins.podmin_email}">#{AppConfig.admins.podmin_email}</a>.
-
-%p
-  %a{href: "javascript:history.back()"}
-    Go Back?

app/views/layouts/error_page.haml

@@ -11,5 +11,12 @@
 
     = yield(:head)
 
-  %body{class: "error-#{@code}", id: "error_#{@code}"}
+  %body{class: "error-#{local_assigns[:code]}", id: "error_#{local_assigns[:code]}"}
+    .transparent.big-number
+      = local_assigns[:code]
+
     = yield
+
+    %p
+      %a{href: "javascript:history.back()"}
+        Go Back?

lib/error_page_renderer.rb

@@ -6,44 +6,14 @@ class ErrorPageRenderer
   def initialize options={}
     @codes    = options.fetch :codes, [404, 500]
     @output   = options.fetch :output, "public/%s.html"
-    @vars     = options.fetch :vars, {}
     @template = options.fetch :template, "errors/error_%s"
     @layout   = options.fetch :layout, "layouts/error_page"
   end
 
   def render
     @codes.each do |code|
-      view = build_action_view
-      view.assign @vars.merge(code: code)
       path = Rails.root.join(@output % code)
-      File.write path, view.render(template: @template % code, layout: @layout)
+      File.write path, ApplicationController.render(@template % code, layout: @layout, locals: {code: code})
     end
   end
-
-  def helpers(&block)
-    @helpers = block
-  end
-
-  private
-
-  def build_action_view
-    paths = ::ActionController::Base.view_paths
-    ::ActionView::Base.new(paths).tap do |view|
-      view.class_eval do
-        include Rails.application.helpers
-        include Rails.application.routes.url_helpers
-      end
-      view.assets_manifest = build_manifest(Rails.application)
-      view.class_eval(&@helpers) if @helpers
-    end
-  end
-
-  # Internal API from the sprocket-rails railtie, if somebody finds a way to
-  # call it, please replace it. Might need to be updated on sprocket-rails
-  # updates.
-  def build_manifest(app)
-    config = app.config
-    path = File.join(config.paths['public'].first, config.assets.prefix)
-    Sprockets::Manifest.new(app.assets, path, config.assets.manifest)
-  end
 end