Point users to the subprocess module in the docs for os.system, os.spawn*, os.popen2, and the popen2 and commands modules

Doc/lib/libcommands.tex

@@ -12,6 +12,11 @@ The \module{commands} module contains wrapper functions for
 return any output generated by the command and, optionally, the exit
 status.
 
+The \module{subprocess} module provides more powerful facilities for
+spawning new processes and retrieving their results.  Using the
+\module{subprocess} module is preferable to using the \module{commands}
+module.
+
 The \module{commands} module defines the following functions:
 
 
@@ -51,3 +56,7 @@ Example:
 >>> commands.getstatus('/bin/ls')
 '-rwxr-xr-x  1 root        13352 Oct 14  1994 /bin/ls'
 \end{verbatim}
+
+\begin{seealso}
+  \seemodule{subprocess}{Module for spawning and managing subprocesses.}
+\end{seealso}