specify what -3 warnings are about

diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index 643464b065d5759548a7168af74263396c111d14..89a3db674b996fd8b06c8b5e67a1afe37d7b5e24 100644 (file)
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -356,7 +356,8 @@ Miscellaneous options
 
 .. cmdoption:: -3
 
-   Warn about Python 3.x incompatibilities. Among these are:
+   Warn about Python 3.x incompatibilities which cannot be fixed trivally by
+   :ref:`2to3 <2to3-reference>`. Among these are:
 
    * :meth:`dict.has_key`
    * :func:`apply`