Executable.__call__ original semantics were to avoid redirecting process output to the output stream if return_output was set. This branch undid that and this commit restores those semantics.
Executable.__call__ original semantics were to avoid redirecting process output
to the output stream if return_output was set. This branch undid that and this
commit restores those semantics.

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