pm-suspend causes computer to shutdown (Dell XPS 15 9550)

[pvh]

Linux kernel version 4.4.0-59-generic. Since a few weeks ago (approximately the start of 2017 I think) suspend, whether triggered by pm-suspend or other means, causes the computer to shutdown, not suspend.

I have tried various kernel options such as "dis_ucode_ldr" and "acpi_sleep=nonvs", suggestions found in various posts on the web, but the behaviour persists.

lsb_release -rd:
Description: Ubuntu 16.04.1 LTS
Release: 16.04

pm-utils:
  Installed: 1.4.1-16
  Candidate: 1.4.1-16
  Version table:
 *** 1.4.1-16 500
        500 http://za.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        500 http://za.archive.ubuntu.com/ubuntu xenial/main i386 Packages
        100 /var/lib/dpkg/status

linux-image-4.4.0-59-generic:
  Installed: 4.4.0-59.80
  Candidate: 4.4.0-59.80
  Version table:
 *** 4.4.0-59.80 500
        500 http://za.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: pm-utils 1.4.1-16
ProcVersionSignature: Ubuntu 4.4.0-59.80-generic 4.4.35
Uname: Linux 4.4.0-59-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Jan 25 22:14:11 2017
EcryptfsInUse: Yes
InstallationDate: Installed on 2016-08-17 (161 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
PackageArchitecture: all
SourcePackage: pm-utils
UpgradeStatus: No upgrade log present (probably fresh install)

[pvh (pvh-webbedfeet)]

Installing bumblebee to support Nvidia Optimus resolved this issue for me.

[pvh (pvh-webbedfeet)]

I don't know how to close this bug, but as noted in #2 it is resolved from my (submitter) perspective.