Remove unused Barrier packet

neo/client/app.py

@@ -1058,9 +1058,6 @@ class Application(object):
         psThreadedPoll()
     close = __del__
 
-    def invalidationBarrier(self):
-        self._askPrimary(Packets.AskBarrier())
-
     def pack(self, t):
         tid = repr(TimeStamp(*time.gmtime(t)[:5] + (t % 60, )))
         if tid == ZERO_TID:

neo/lib/handler.py

@@ -133,12 +133,6 @@ class EventHandler(object):
     def notify(self, conn, message):
         neo.lib.logging.info('notification from %r: %s', conn, message)
 
-    def askBarrier(self, conn):
-        conn.answer(Packets.AnswerBarrier())
-
-    def answerBarrier(self, conn):
-        pass
-
     # Error packet handlers.
 
     def error(self, conn, code, message):

neo/lib/protocol.py

@@ -1245,15 +1245,6 @@ class CheckCurrentSerial(Packet):
         PTID('serial'),
     )
 
-class Barrier(Packet):
-    """
-    Initates a "network barrier", allowing the node sending this packet to know
-    when all packets sent previously on the same connection have been handled
-    by its peer.
-    """
-
-    _answer = PFEmpty
-
 class Pack(Packet):
     """
     Request a pack at given TID.
@@ -1525,8 +1516,7 @@ class Packets(dict):
             0x002B, TIDListFrom)
     AskObjectHistoryFrom, AnswerObjectHistoryFrom = register(
             0x002C, ObjectHistoryFrom)
-    AskBarrier, AnswerBarrier = register(
-            0x002D, Barrier)
+    # 2D
     AskPack, AnswerPack = register(
             0x002E, Pack, ignore_when_closed=False)
     AskCheckTIDRange, AnswerCheckTIDRange = register(