spack setup : improved error message
spack setup : improved error message

mfherbst/spack,tmerrick1/spack,EmreAtes/spack,iulian787/spack,lgarren/spack,mfherbst/spack,LLNL/spack,mfherbst/spack,EmreAtes/spack,EmreAtes/spack,krafczyk/spack,skosukhin/spack,matthiasdiener/spack,iulian787/spack,krafczyk/spack,krafczyk/spack,skosukhin/spack,iulian787/spack,krafczyk/spack,tmerrick1/spack,TheTimmy/spack,skosukhin/spack,krafczyk/spack,TheTimmy/spack,TheTimmy/spack,matthiasdiener/spack,matthiasdiener/spack,tmerrick1/spack,EmreAtes/spack,mfherbst/spack,EmreAtes/spack,matthiasdiener/spack,LLNL/spack,LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack,lgarren/spack,matthiasdiener/spack,lgarren/spack,LLNL/spack,lgarren/spack,TheTimmy/spack,mfherbst/spack,lgarren/spack,tmerrick1/spack,skosukhin/spack,TheTimmy/spack,skosukhin/spack,tmerrick1/spack