Handle errors using Gaffe

config/locales/en.yml

@@ -638,6 +638,13 @@ en:
     general: A problem has occured.
     general_again: A problem has occured. Please try again.
     general_msg: 'A problem has occured: %{msg}'
+    not_found:
+      title: Page not found
+      text: This page does not appear to exist, sorry!
+    internal_server_error:
+      title: Internal server error
+      text1: An unexpected error has occured. Sorry!
+      text2: We've been notified. If this remains a problem, please tell us so.
   feedback:
     create:
       notice: Your feedback was sent successfully. Thanks a lot!
@@ -771,10 +778,8 @@ en:
       linked_delivery: a delivery
       linked_order: an order
       new:
-        back: Back
         title: Create new invoice
       show:
-        back: Back
         title: Invoice %{number}
     ordergroups:
       index:
@@ -1685,6 +1690,7 @@ en:
       title_all: All group tasks
   ui:
     actions: Actions
+    back: Back
     cancel: Cancel
     close: Close
     copy: Copy