Improved paragraph on __path__ recalculation. Suggested by Nick Coglan.

pep-0420.txt

@@ -125,8 +125,11 @@ package:
  * Has a __path__ set to the list of directories there were found and
    recorded during the scan.
 
-There is no mechanism to recompute the __path__ once a namespace
-package has been created.
+There is no mechanism to automatically recompute the ``__path__`` if
+``sys.path`` is altered after a namespace package has already been
+created. However, existing namespace utilities (like
+``pkgutil.extend_path()``) can be used to update them explicitly if
+desired.
 
 Note that if "import foo" is executed and "foo" is found as a
 namespace package (using the above rules), then "foo" is immediately