no-store hint

otr.py

@@ -176,4 +176,5 @@ class OTR(context.Account):
             event.encrypted, event.additional_data["encrypted"] = OTR.ENCRYPTION_NAME, {"name":OTR.ENCRYPTION_NAME} # some mandatory encryption flags
             if channel.resource:
                 event.stanza.addChild('no-copy', namespace='urn:xmpp:hints') # don't send carbons
+                event.stanza.addChild('no-store', namespace='urn:xmpp:hints') # don't store in MAM
             callback(event)