diff -r 4e72b78ea5aa -r 9d6a34b9838d server/session.py
--- a/server/session.py	Fri Mar 22 20:05:49 2013 +0100
+++ b/server/session.py	Fri Mar 22 19:58:43 2013 +0100
@@ -417,6 +417,7 @@
 
     @property
     def _tx(self):
+        """default transaction for current session in current thread"""
         try:
             return self.__threaddata.tx
         except AttributeError: