Minor fixups to some index entries.

Doc/ref/ref7.tex

@@ -239,9 +239,10 @@ threaded program.  As of Python 1.5, the variables are restored to
 their previous values (before the call) when returning from a function
 that handled an exception.
 \refbimodindex{sys}
-\ttindex{exc_type}
-\ttindex{exc_value}
-\ttindex{exc_traceback}
+\withsubitem{(in module sys)}{%
+  \ttindex{exc_type}%
+  \ttindex{exc_value}%
+  \ttindex{exc_traceback}}
 \obindex{traceback}
 
 The optional \keyword{else} clause is executed when no exception occurs