packer.json crash

packer.json

{
  "variables": {
    "azure_client_secret": "{{env `AZURE_CLIENT_SECRET`}}",
    "aws_access_key": "{{env `AWS_ACCESS_KEY`}}",
    "aws_secret_key": "{{env `AWS_SECRET_KEY`}}",
    "datadog_api_key": "{{env `DATADOG_API_KEY`}}"
  },

  "builders": [
    {
    "type": "amazon-ebs",
    "ami_name": "nodejs {{timestamp}}",
    "ami_description": "Ubuntu 16.04, nginx 1.10.3, Node.js 8.x LTS",
    "access_key": "{{user `aws_access_key`}}",
    "secret_key": "{{user `aws_secret_key`}}",
    "region": "{{user `aws_region`}}",
    "source_ami": "ami-08660f1c6fb6b01e7", 
    "instance_type": "m3.medium",
    "ssh_username": "ubuntu",
    "launch_block_device_mappings": [{
        "delete_on_termination": true,
        "device_name": "/dev/xvdf",
        "encrypted": false,
        "volume_size": 50,
        "volume_type": "gp2"
      }]
    },
    {
      "type": "azure-arm",
      "client_id": "{{ user `client_id`}}",
      "client_secret": "{{user `azure_client_secret`}}",
      "managed_image_name": "node-{{timestamp}}",
      "managed_image_resource_group_name": "{{ user `resource_group_name` }}",
      "build_resource_group_name": "{{ user `resource_group_name` }}",
      "subscription_id": "{{ user `subscription_id` }}",
      "tenant_id": "{{ user `tenant_id` }}",
      "os_type": "Linux",
      "image_publisher": "Canonical",
      "image_offer": "UbuntuServer",
      "image_sku": "16.04-LTS",
      "vm_size": "Standard_A2_V2",
      "os_disk_size_gb": "30",
      "disk_additional_size": ["50"],
      "azure_tags": {
        "type": "node",
        "createdBy": "packer"
      }
  }
],
  "provisioners": [
    {
      "type": "shell",
      "script": "setup/_common.sh",
      "environment_vars": ["DATADOG_API_KEY={{ user `datadog_api_key` }}"]
    },
    {
      "type": "shell",
      "script": "setup/aws.sh",
      "only": ["amazon-ebs"]
    },
    {
      "type": "shell",
      "script": "setup/azure.sh",
      "only": ["azure-arm"]
    },
    {
      "type": "shell",
      "script": "post/_common.sh"
    },
    {
      "type": "shell",
      "script": "post/azure.sh",
      "only": ["azure-arm"]
    }
  ],
  "post-processors": [
    {
      "type": "manifest",
      "output": "manifest.json",
      "strip_path": true
    }
  ]
}