doc of PYTHONFAULTHANDLER env var: add missing "versionadded" tag
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index f2d2616..4e7168f 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -562,6 +562,8 @@
    Python traceback.  This is equivalent to :option:`-X` ``faulthandler``
    option.
 
+   .. versionadded:: 3.3
+
 
 Debug-mode variables
 ~~~~~~~~~~~~~~~~~~~~