Add missing 'history_tail_reply' signal to QtKernelManager.

IPython/frontend/qt/kernelmanager.py

@@ -46,6 +46,7 b' class QtXReqSocketChannel(SocketChannelQObject, XReqSocketChannel):'
     execute_reply = QtCore.Signal(object)
     complete_reply = QtCore.Signal(object)
     object_info_reply = QtCore.Signal(object)
+    history_tail_reply = QtCore.Signal(object)
 
     # Emitted when the first reply comes back.
     first_reply = QtCore.Signal()