Throw a more user-friendly exception if user selects an unsupported attribute.
Throw a more user-friendly exception if user selects an unsupported
attribute.

nzlosh/st2,nzlosh/st2,StackStorm/st2,Plexxi/st2,Plexxi/st2,Plexxi/st2,nzlosh/st2,nzlosh/st2,StackStorm/st2,StackStorm/st2,StackStorm/st2,Plexxi/st2