Clearer description of Response.close().

requests/models.py

@@ -791,8 +791,8 @@ class Response(object):
             raise HTTPError(http_error_msg, response=self)
 
     def close(self):
-        """Closes the underlying file descriptor and releases the connection
-        back to the pool.
+        """Releases the connection back to the pool. Once this method has been
+        called the underlying ``raw`` object must not be accessed again.
 
         *Note: Should not normally need to be called explicitly.*
         """