juju bootstrap stuck in "Running apt-get upgrade"

[Francis Ginther]

Was bootstrapping to a juju environment on an Landscape Autopilot deployed openstack cloud which uses an http/https proxy. This generally works, but on this case the bootstrap appeared to be stuck at "Running apt-get upgrade"

I was able to ssh into the instance and saw that the following apt-get command kept recurring:

apt-get --option=Dpkg::Options::=--force-confold --option=Dpkg::options::=--force-unsafe-io --assume-yes --quiet upgrade

Running this manually showed:
$ sudo apt-get --option=Dpkg::Options::=--force-confold --option=Dpkg::options::=--force-unsafe-io --assume-yes --quiet upgrade
sudo: unable to resolve host juju-lsci-cloud-machine-0
Reading package lists...
Building dependency tree...
Reading state information...
The following packages will be upgraded:
  libcgmanager0 screen
2 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 567 kB of archives.
After this operation, 67.6 kB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
  libcgmanager0 screen
E: There are problems and -y was used without --force-yes

A google of the WARNING message brought me to [1] which suggested doing:

sudo apt-key update

Shortly after running the "apt-key update" command, the "apt-get upgrade" started working and the bootstrap completed with no other issues.

[1] - http://askubuntu.com/questions/75565/why-am-i-getting-authentication-errors-for-packages-from-an-ubuntu-repository

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: juju-1.25 1.25.5-0ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-22.39-generic 4.4.8
Uname: Linux 4.4.0-22-generic x86_64
NonfreeKernelModules: kpatch_livepatch_Ubuntu_4_4_0_22_39_generic_7 kpatch_livepatch_Ubuntu_4_4_0_22_39_generic_5 nvidia_uvm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Jun 1 13:20:00 2016
InstallationDate: Installed on 2016-04-24 (38 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: juju-core-1
UpgradeStatus: No upgrade log present (probably fresh install)