show dependency validation errors in action edit form

app/controllers/todos_controller.rb

@@ -423,7 +423,16 @@ class TodosController < ApplicationController
     update_dependencies
     update_attributes_of_todo
 
-    @saved = @todo.save
+    begin
+      @saved = @todo.save!
+    rescue ActiveRecord::RecordInvalid => exception
+      record = exception.record
+      if record.is_a?(Dependency)
+        record.errors.each { |key,value| @todo.errors[key] << value }
+      end
+      @saved = false
+    end
+
 
     # this is set after save and cleared after reload, so save it here
     @removed_predecessors = @todo.removed_predecessors