Add optional 'onerror' argument to os.walk(), to control error
handling.
diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index dd492bb..074d332 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -1054,7 +1054,8 @@
Availability: Macintosh, \UNIX, Windows.
\end{funcdesc}
-\begin{funcdesc}{walk}{top\optional{, topdown\code{=True}}}
+\begin{funcdesc}{walk}{top\optional{, topdown\code{=True}
+ \optional{, onerror\code{=None}}}}
\index{directory!walking}
\index{directory!traversal}
\function{walk()} generates the file names in a directory tree, by
@@ -1087,6 +1088,13 @@
false is ineffective, because in bottom-up mode the directories in
\var{dirnames} are generated before \var{dirnames} itself is generated.
+By default errors from the \code{os.listdir()} call are ignored. If
+optional argument \var{onerror} is specified, it should be a function;
+it will be called with one argument, an os.error instance. It can
+report the error to continue with the walk, or raise the exception
+to abort the walk. Note that the filename is available as the
+\code{filename} attribute of the exception object.
+
\begin{notice}
If you pass a relative pathname, don't change the current working
directory between resumptions of \function{walk()}. \function{walk()}