Mark deprecated modules as such.
diff --git a/Doc/library/popen2.rst b/Doc/library/popen2.rst
index d685785..826dff0 100644
--- a/Doc/library/popen2.rst
+++ b/Doc/library/popen2.rst
@@ -4,6 +4,7 @@
 
 .. module:: popen2
    :synopsis: Subprocesses with accessible standard I/O streams.
+   :deprecated:
 .. sectionauthor:: Drew Csillag <drew_csillag@geocities.com>