added checks for the *_content_type, *_file_size and *_updated_at col…

…umns

lib/paperclip/attachment.rb

@@ -54,7 +54,7 @@ def initialize name, instance, options = {}
     # In addition to form uploads, you can also assign another Paperclip attachment:
     #   new_user.avatar = old_user.avatar
     def assign uploaded_file
-      %w(file_name).each do |field|
+      %w(file_name content_type file_size updated_at).each do |field|
         unless @instance.class.column_names.include?("#{name}_#{field}")
           raise PaperclipError.new("#{@instance.class} model does not have required column '#{name}_#{field}'")
         end