now remove a non empty directory

lib/tasks/attachment_maintaining_service.rake

+require 'fileutils'
+
   namespace :attachment_maintaining_service do
     desc 'Removing 10 attachments'
     task remove_attachments: :environment do
       m = sort_directories.first(10)
       m.each do |mm|
-        rmdir(mm)
+        puts (mm)
+        FileUtils.rm_r(mm)
       end
     end