re-enable use_session=True,

some problems saving network messages::

   File "/usr/local/src/x84/x84/default/writemsg.py", line 422, in main
     msg.save()

   File "x84/bbs/msgbase.py", line 154, in save
     for tag, msgs in db_tag.iteritems():

   File "/usr/local/lib/python2.7/dist-packages/sqlitedict.py", line 140, in iteritems
     for key, value in self.conn.select(GET_ITEMS):

 AttributeError: 'NoneType' object has no attribute 'select'