make null source work in local/test mode.
make null source work in local/test mode.

cchepelov/scalding,lucamilanesio/scalding,twitter/scalding,bendridi/scalding,f7753/scalding,cauchycui/scalding,sid-kap/scalding,aposwolsky/scalding,tresata/scalding,piyushnarang/scalding,bmyerz/scalding,tdyas/scalding,jzmq/scalding,avp1984/scalding,tresata/scalding,aposwolsky/scalding,avp1984/scalding,chrismoulton/scalding,jzmq/scalding,sid-kap/scalding,nkhuyu/scalding,Chasego/scalding,sunilrebel/scalding,sriramkrishnan/scalding,JiJiTang/scalding,rubanm/scalding,oeddyo/scalding,rjhall/etsy.scalding,zirpins/scalding,cauchycui/scalding,chrismoulton/scalding,benpence/scalding,Chasego/scalding,avp1984/scalding,sunilrebel/scalding,bendridi/scalding,MansurAshraf/scalding,nvoron23/scalding,AaroC357/scalding,twitter/scalding,stripe/scalding,piyushnarang/scalding,danosipov/scalding,zirpins/scalding,aposwolsky/scalding,sunilrebel/scalding,AaroC357/scalding,wanyifu/scaldingtest,tdyas/scalding,sriramkrishnan/scalding,nkhuyu/scalding,wanyifu/scaldingtest,epishkin/scalding,stripe/scalding,twitter/scalding,benpence/scalding,JiJiTang/scalding,lucamilanesio/scalding,oeddyo/scalding,wanyifu/scaldingtest,epishkin/scalding,bmyerz/scalding,tdyas/scalding,tglstory/scalding,cchepelov/scalding,danosipov/scalding,sid-kap/scalding,f7753/scalding,danosipov/scalding,rjhall/etsy.scalding,nkhuyu/scalding,Chasego/scalding,benpence/scalding,piyushnarang/scalding,MansurAshraf/scalding,jzmq/scalding,zirpins/scalding,cchepelov/scalding,chrismoulton/scalding,soundcloud/scalding,cauchycui/scalding,soundcloud/scalding,tglstory/scalding,rubanm/scalding,bmyerz/scalding,vidyar/twitterscalding,oeddyo/scalding,AaroC357/scalding,tglstory/scalding,nvoron23/scalding,JiJiTang/scalding,vidyar/twitterscalding,MansurAshraf/scalding,lucamilanesio/scalding,bendridi/scalding,tresata/scalding,rubanm/scalding,f7753/scalding,nvoron23/scalding,sriramkrishnan/scalding,soundcloud/scalding