django-scarface strange message trimmed on iOS push notification

I have a strange issue about iOS push notification and my django app.

In my djnago application I integrated django-scarface to send push notification to iOS and Android device using Amazon AWS SNS service.

In my test I can send push notifications to a generic device using a string message. I can receive correctly all notifications on my devices.

Now, if I change the text of notification like this:

notification_message = notifications.settings.REQUEST_RECEIVED_NOTIFICATION_MESSAGE % sender.from_user.first_name

REQUEST_RECEIVED_NOTIFICATION_MESSAGE = "%s sent you a request!"

notification_message is correctly generated... for example I read u"Safari sent you a request!" (in debug mode) but, when I receive the notification on iOS device I have something like this:

"Safari sent you...."

For some strange region my message is trimmed...

But, If I set hardcoded the name all works well: for example, if I have:

notification_message = notifications.settings.REQUEST_RECEIVED_NOTIFICATION_MESSAGE % "SAFARI"

Have you some suggestion about this strange problem?