fix for issue 398, added extensions_for in RepoPath
fix for issue 398, added extensions_for in RepoPath

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