Fail early in task argument parsing (again)
Fail early in task argument parsing (again)

This reduces indentation for the begin end while loop.

askl56/rake,ipmobiletech/rake,pjump/rake,envato/rake,utilum/rake,envato/rake,Vanzct/rake,88rabbit/rake,esasse/rake,jaustinhughey/rake,ruby/rake,codedogfish/rake,zzak/rake,tmornini/rake,ruby/rake,bentley/rake,taiganakagawa/rake