Fix failure on middleware/exceptions_test

The reason the test was failing was because when the test
invokes `app.config`, the app is loaded and, as `eager_load`
is set to true, it disables the dependency loading mechanism,
so controllers that are later defined are not loaded.

railties/lib/rails/application/finisher.rb

@@ -91,7 +91,7 @@ module Finisher
 
       # Disable dependency loading during request cycle
       initializer :disable_dependency_loading do
-        if config.eager_load
+        if config.eager_load && config.cache_classes
           ActiveSupport::Dependencies.unhook!
         end
       end

railties/test/application/middleware/exceptions_test.rb

@@ -88,9 +88,6 @@ def index
     end
 
     test "displays diagnostics message when exception raised in template that contains UTF-8" do
-      app.config.action_dispatch.show_exceptions = true
-      app.config.consider_all_requests_local = true
-
       controller :foo, <<-RUBY
         class FooController < ActionController::Base
           def index
@@ -98,18 +95,15 @@ def index
         end
       RUBY
 
+      app.config.action_dispatch.show_exceptions = true
+      app.config.consider_all_requests_local = true
+
       app_file 'app/views/foo/index.html.erb', <<-ERB
         <% raise 'boooom' %>
         ✓測試テスト시험
       ERB
 
-      app_file 'config/routes.rb', <<-RUBY
-        AppTemplate::Application.routes.draw do
-          post ':controller(/:action)'
-        end
-      RUBY
-
-      post '/foo', :utf8 => '✓'
+      get '/foo', :utf8 => '✓'
       assert_match(/boooom/, last_response.body)
       assert_match(/測試テスト시험/, last_response.body)
     end