I setup the Automatic Security Updates on Ubuntu OS with unattended-upgrades packages using a Ansible playbook. For more info about unattended-upgrades go to debian wiki or ubuntu help.

~$ sudo ansible-galaxy install jnv.unattended-upgrades

~$ vi unattended-upgrades.yml

    - hosts: unattended_hosts
        admin_mail: "user@company.com"
      - role: jnv.unattended-upgrades
        - 'origin=Ubuntu,archive=${distro_codename}-security'
        - 'o=Ubuntu,a=${distro_codename}-updates'
        unattended_package_blacklist: [cowsay, vim]
~$ vi ansible_hosts

    remote-host.company.com    ansible_connection=ssh  ansible_ssh_user=root
~$ ansible-playbook -i ansible_hosts unattended-upgrades.yml

~$ ssh user@remote-host
~$ sudo unattended-upgrade --debug --dry-run

        Initial blacklisted packages: cowsay vim
        Starting unattended upgrades script
        Allowed origins are: ['origin=Ubuntu,archive=trusty-security', 'o=Ubuntu,a=trusty-updates']
        pkgs that look like they should be upgraded: 
        Fetched 0 B in 0s (0 B/s)                                                                                                
        fetch.run() result: 0
        blacklist: ['cowsay', 'vim']
        No packages found that can be upgraded unattended and no pending auto-removals

I have this issue after apply this playbook, and found the solution on ubuntu forums.

~# apt-get update

    Hit http://security.ubuntu.com trusty-security InRelease                       
    Hit http://security.ubuntu.com trusty-security/main amd64 Packages
    Hit http://security.ubuntu.com trusty-security/main Translation-en  
    Fetched 14 B in 17s (0 B/s)                                                    
    Reading package lists... Done
    N: Ignoring file '20auto-upgrades.ucf-dist' in directory '/etc/apt/apt.conf.d/' as it has an invalid filename extension

~# diff /etc/apt/apt.conf.d/20auto-upgrades.ucf-dist /etc/apt/apt.conf.d/20auto-upgrades

    < APT::Periodic::Update-Package-Lists "0";
    < APT::Periodic::Unattended-Upgrade "0";
    > APT::Periodic::Update-Package-Lists "1";
    > APT::Periodic::Download-Upgradeable-Packages "1";
    > APT::Periodic::AutocleanInterval "7";
    > APT::Periodic::Unattended-Upgrade "1";

~# rm /etc/apt/apt.conf.d/20auto-upgrades.ucf-dist