provisioner/powershell: fix dropped error
provisioner/powershell: fix dropped error

provisioner/powershell: improve error message

rnaveiras/packer,hashicorp/packer,rnaveiras/packer,rnaveiras/packer,mitchellh/packer,grubernaut/packer,ricardclau/packer,ricardclau/packer,mitchellh/packer,ricardclau/packer,rnaveiras/packer,grubernaut/packer,rnaveiras/packer,pecigonzalo/packer,hashicorp/packer,grubernaut/packer,pecigonzalo/packer,pecigonzalo/packer,mitchellh/packer,ricardclau/packer,grubernaut/packer,ricardclau/packer,grubernaut/packer,hashicorp/packer,mitchellh/packer,rnaveiras/packer,grubernaut/packer,pecigonzalo/packer,hashicorp/packer,ricardclau/packer,mitchellh/packer