travis: fixes failure on six (#4415)
travis: fixes failure on six (#4415)


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