Error when selecting non-existing config

[chuckha]

Right now you can use any string with ktx. It should, at the very least, let you know that that file does not exist.

Example:

 salazar:~ cha$ ktx 
dev    prod   test
 salazar:~ cha$ eval $(ktx hello-world)
hello-world salazar:~ cha$ 

Expected result

 salazar:cluster-config cha$ eval $(ktx hello-world)
File does not exist! Not doing anything.