Don't fire displayhook on input==None (match python default)
Don't fire displayhook on input==None (match python default)

swn1/pyzmq,caidongyun/pyzmq,caidongyun/pyzmq,Mustard-Systems-Ltd/pyzmq,swn1/pyzmq,Mustard-Systems-Ltd/pyzmq,ArvinPan/pyzmq,dash-dash/pyzmq,yyt030/pyzmq,dash-dash/pyzmq,dash-dash/pyzmq,ArvinPan/pyzmq,swn1/pyzmq,caidongyun/pyzmq,yyt030/pyzmq,yyt030/pyzmq,ArvinPan/pyzmq,Mustard-Systems-Ltd/pyzmq