improve view decorator return type documentation

Fixes #2770.

docs/narr/viewconfig.rst

@@ -252,16 +252,18 @@ Non-Predicate Arguments
     def myview(request):
       ...
 
-  Is similar to doing::
+  Is similar to decorating the view callable directly::
 
     @view_config(...)
     @decorator2
     @decorator1
     def myview(request):
       ...
 
-  All view callables in the decorator chain must return a response object
-  implementing :class:`pyramid.interfaces.IResponse` or raise an exception:
+  An important distinction is that each decorator will receive a response
+  object implementing :class:`pyramid.interfaces.IResponse` instead of the
+  raw value returned from the view callable. All decorators in the chain must
+  return a response object or raise an exception:
 
   .. code-block:: python
 

pyramid/config/views.py

@@ -444,9 +444,11 @@ def myview(request):
           think about preserving function attributes such as ``__name__`` and
           ``__module__`` within decorator logic).
 
-          All view callables in the decorator chain must return a response
-          object implementing :class:`pyramid.interfaces.IResponse` or raise
-          an exception:
+          An important distinction is that each decorator will receive a
+          response object implementing :class:`pyramid.interfaces.IResponse`
+          instead of the raw value returned from the view callable. All
+          decorators in the chain must return a response object or raise an
+          exception:
 
           .. code-block:: python