I modified the JSON to work with debian 9. I have no idea how to create a new pull request. Including source code mods:
"boot_wait": "5s",
"disk_size": 81920,
"guest_os_type": "debian8-64",
"headless": true,
"http_directory": "http",
"iso_urls": [
"iso/debian-9.1.0-amd64-xfce-CD-1.iso",
"https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-9.1.0-amd64-xfce-CD-1.iso"
],
"iso_checksum_type": "sha256",
"iso_checksum": "9558262f6c15b024d8c3ca140d1c70c310f11384e227329d08dab38c915a4306",
"output_directory": "packer-debian-9-amd64-vmware",
"shutdown_command": "echo 'vagrant'|sudo -S shutdown -P now",
"ssh_password": "vagrant",
"ssh_port": 22,
"ssh_username": "vagrant",
"ssh_wait_timeout": "10000s",
"tools_upload_flavor": "linux",
"vm_name": "packer-debian-9-amd64",
"vmx_data": {
"cpuid.coresPerSocket": "1",
"ethernet0.pciSlotNumber": "32",
"memsize": "1024",
"numvcpus": "1"