better exception message for missing arg
better exception message for missing arg

PeterWangPo/stylus,a-x-/stylus,meteor/stylus,peterkinalex/stylus-1,HossainKhademian/Stylus,angryrobot/stylus,isaacs/stylus,rstacruz/stylus,behzad88/stylus,silvaemota/stylus,Delapouite/stylus,SimenB/stylus,jameswomack/stylus,modulexcite/stylus,darwin/stylus,stylus/stylus,baotingfang/stylus,Ricardh522/stylus,galenvagen/stylus,johnnycopperstone/stylus,Zagorakiss/stylus,jangarcia/stylus,cemoulto/stylus,yetone/stylus,ThiagoGarciaAlves/stylus,Panya/stylus,tyv/stylus,trixter5/stylus,jonpacker/stylus