Clarify "raised inside REST framework"

I ran into an issue today where I was not seeing the rest_framework.views.exception_handler do what I thought it should be doing. It turned out that I had imported View from rest_framework.views rather than importing APIView from rest_framework.views. The phrase "raised inside REST framework" was confusing as I was debugging this issue. I was unsure if that meant that I could raise those exceptions in my code or if it had to originate from within framework code.

I'm not sure if the proposed wording is ideal, I just wanted to point out what I found to be confusing.
Fixed code formatting
Merge pull request #1882 from mattjmorrison/patch-2

Clarify "raised inside REST framework"