chore: Ease debugging errors with dummy app

Do not show formatted HTML error pages but raise errors up.

Author: jgraichen

spec/dummy/config/environments/test.rb

@@ -21,7 +21,7 @@
   config.action_controller.perform_caching = false
 
   # Raise exceptions instead of rendering exception templates.
-  config.action_dispatch.show_exceptions = false
+  config.action_dispatch.show_exceptions = :none
 
   # Disable request forgery protection in test environment.
   config.action_controller.allow_forgery_protection = false