code: def activate_users(self, request, queryset):
          
          n = 0
          for user in queryset:
              if not user.is_active:
                  user.activate()
                  n += 1
          self.message_user(
              request,
              _('Successfully activated %(count)d %(items)s.') %
              {'count': n, 'items': model_ngettext(self.opts, n)},  messages.SUCCESS)
docs: Activates the selected users, if they are not already
          activated.