Document clearly that the only way to retrieve the return code from the
child processes is to use the Popen3 and Popen4 classes.
This fixes SF bug #460512.
diff --git a/Doc/lib/libpopen2.tex b/Doc/lib/libpopen2.tex
index add0af1..8cdf0f5 100644
--- a/Doc/lib/libpopen2.tex
+++ b/Doc/lib/libpopen2.tex
@@ -24,6 +24,13 @@
in binary or text mode. The default value for \var{mode} is
\code{'t'}.
+The only way to retrieve the return codes for the child processes is
+by using the \method{poll()} or \method{wait()} methods on the
+\class{Popen3} and \class{Popen4} classes; these are only available on
+\UNIX. This information is not available when using the
+\function{popen2()}, \function{popen3()}, and \function{popen4()}
+functions, or the equivalent functions in the \refmodule{os} module.
+
\begin{funcdesc}{popen2}{cmd\optional{, bufsize\optional{, mode}}}
Executes \var{cmd} as a sub-process. Returns the file objects
\code{(\var{child_stdout}, \var{child_stdin})}.