Add stream feature for server support of subscription pre-approvals.

sleekxmpp/features/feature_preapproval/stanza.py

@@ -0,0 +1,17 @@
+"""
+    SleekXMPP: The Sleek XMPP Library
+    Copyright (C) 2012  Nathanael C. Fritz
+    This file is part of SleekXMPP.
+
+    See the file LICENSE for copying permission.
+"""
+
+from sleekxmpp.xmlstream import ElementBase
+
+
+class PreApproval(ElementBase):
+
+    name = 'sub'
+    namespace = 'urn:xmpp:features:pre-approval'
+    interfaces = set()
+    plugin_attrib = 'preapproval'