Imagine you write software for rabbit-mq. But then you get a requirements change to use zero-mq for whatever reason. Is that deviance? Have you normalized it? No, and no.
Deviance is when you're dropping messages in production when you shouldn't. Normalizing is when you ignore it because "it's usually fine".
You're probably thinking that my analogy doesn't work because changing software libraries is different than accepting an out of spec part. But why? If it's out of spec, it's a different part. You can make a spec around that part and design to it all the same. Just because it wasn't your first choice doesn't mean it's dangerous.