Packer Build Issue

{
  "builders": [
    {
      "access_key": "{{user `var_aws_access_key`}}",
      "ami_description": "My new AMI",
      "ami_name": "CentOS 7 x86_64 Base {{timestamp}}",
      "associate_public_ip_address": true,
      "enhanced_networking": true,
      "instance_type": "{{user `var_aws_instance_type`}}",
      "region": "{{user `var_aws_region`}}",
      "secret_key": "{{user `var_aws_secret_key`}}",
      "source_ami": "{{user `var_aws_source_ami`}}",
      "ssh_private_ip": false,
      "ssh_pty": true,
      "ssh_username": "{{user `var_ssh_username`}}",
      "subnet_id": "{{user `var_aws_subnet_id`}}",
      "tags": {
        "Built": "{{isotime \"01-02-2006\"}}",
        "Name": "{{user `var_atlas_buildname`}}",
        "OS_Family": "RedHat",
        "OS_Version": "CentOS",
        "Release": "7"
      },
      "type": "amazon-ebs",
      "vpc_id": "{{user `var_aws_vpc_id`}}"
    }
  ],
  "description": "My New AMI",
  "min_packer_version": "0.10.2",
  "post-processors": [
    {
      "artifact": "{{user `var_atlas_username`}}/{{user `var_atlas_buildname`}}",
      "artifact_type": "amazon.image",
      "metadata": {
        "created_at": "{{timestamp}}"
      },
      "only": [
        "amazon-ebs"
      ],
      "token": "{{user `var_atlas_token`}}",
      "type": "atlas"
    }
  ],
  "provisioners": [
    {
      "inline": [
        "while [ ! -f /var/lib/cloud/instance/boot-finished ]; do echo 'Waiting for cloud-init...'; sleep 1; done"
      ],
      "type": "shell"
    },
    {
      "execute_command": "sudo -E -S sh '{{ .Path }}'",
      "scripts": [
        "scripts/install_packages.sh",
        "scripts/install_packages.sh"
      ],
      "type": "shell"
    }
  ],
  "push": {
    "name": "{{user `var_atlas_username`}}/{{user `var_atlas_buildname`}}",
    "vcs": false
  },
  "variables": {
    "var_atlas_buildname": "my-new-ami",
    "var_atlas_token": "{{env `ATLAS_TOKEN`}}",
    "var_atlas_username": "{{env `ATLAS_USERNAME`}}",
    "var_aws_access_key": "{{env `AWS_ACCESS_KEY_ID`}}",
    "var_aws_instance_type": "t2.micro",
    "var_aws_region": "us-east-1",
    "var_aws_secret_key": "{{env `AWS_SECRET_ACCESS_KEY`}}",
    "var_aws_source_ami": "XXXXXXXXXXXXXXXX",
    "var_aws_subnet_id": "XXXXXXXXXXXXXXX",
    "var_aws_vpc_id": "XXXXXXXXXXXXXXXX",
    "var_ssh_username": "XXXXXXXXXXXXXX"
  }
}








############################



$ cat scripts/install_packages.sh 
#!/bin/bash
set -o pipefail
set -x
echo "+) Updating system packages"
yum makecache
yum update -y