Use #unscoped or #with_exclusive_scope when selecting records for the rake task

lib/paperclip.rb

@@ -140,10 +140,13 @@ module Paperclip
     # Find all instances of the given Active Record model +klass+ with attachment +name+.
     # This method is used by the refresh rake tasks.
     def each_instance_with_attachment(klass, name)
+      unscope_method = class_for(klass).respond_to?(:unscoped) ? :unscoped : :with_exclusive_scope
+      class_for(klass).send(unscope_method) do
         class_for(klass).find(:all, :order => 'id').each do |instance|
           yield(instance) if instance.send(:"#{name}?")
         end
       end
+    end
 
     # Log a paperclip-specific line. This will logs to STDOUT
     # by default. Set Paperclip.options[:log] to false to turn off.