exclude cancelled presentations from being slotted
exclude cancelled presentations from being slotted

pyohio/symposion,euroscipy/symposion,toulibre/symposion,toulibre/symposion,pyconau2017/symposion,miurahr/symposion,pyconau2017/symposion,miurahr/symposion,mbrochh/symposion,TheOpenBastion/symposion,pyohio/symposion,python-spain/symposion,NelleV/pyconfr-test,NelleV/pyconfr-test,mbrochh/symposion,euroscipy/symposion,python-spain/symposion,pyconca/2013-web,faulteh/symposion,TheOpenBastion/symposion,pydata/symposion,pydata/symposion,pyconca/2013-web,pinax/symposion,faulteh/symposion,pinax/symposion