Execute modulecmd in bash shell (#11510)
Execute modulecmd in bash shell (#11510)

Adds executable=/bin/bash into Popen. We discovered this bug while
working in a csh/tsch environment. By executing with /bin/bash we ensure
that the module command works.
iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack,LLNL/spack,LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack