charm failure to install - The following packages cannot be authenticated

I am seeing a number of charms failing to install because of authentication failure during package install. It retries a few times. I have observed it for multiple charms so thinking this may be a charm helpers issue.

This is from unit log for contrail-webui:

2015-09-14 14:22:50 DEBUG worker.uniter.jujuc server.go:159 hook context id "contrail-webui/0-install-414841784440951436"; dir "/var/lib/juju/agents/unit-contrail-webui-0/charm"
2015-09-14 14:22:50 INFO juju-log Couldn't acquire DPKG lock. Will retry in 10 seconds.
2015-09-14 14:22:58 DEBUG juju.worker.leadership tracker.go:138 contrail-webui/0 renewing lease for contrail-webui leadership
2015-09-14 14:22:58 DEBUG juju.worker.leadership tracker.go:165 checking contrail-webui/0 for contrail-webui leadership
2015-09-14 14:22:59 DEBUG juju.worker.leadership tracker.go:180 contrail-webui/0 confirmed for contrail-webui leadership until 2015-09-14 14:23:58.148047419 +0000 UTC
2015-09-14 14:22:59 INFO juju.worker.leadership tracker.go:182 contrail-webui/0 will renew contrail-webui leadership at 2015-09-14 14:23:28.148047419 +0000 UTC
2015-09-14 14:23:00 INFO install Reading package lists...
2015-09-14 14:23:01 INFO install Building dependency tree...
2015-09-14 14:23:01 INFO install Reading state information...
2015-09-14 14:23:01 INFO install The following packages were automatically installed and are no longer required:
2015-09-14 14:23:01 INFO install libfreetype6 os-prober
2015-09-14 14:23:01 INFO install Use 'apt-get autoremove' to remove them.
2015-09-14 14:23:01 INFO install The following packages will be upgraded:
2015-09-14 14:23:01 INFO install bind9-host dnsutils libbind9-90 libdns100 libisc95 libisccc90 libisccfg90
2015-09-14 14:23:01 INFO install liblwres90
2015-09-14 14:23:01 INFO install 8 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2015-09-14 14:23:01 INFO install Need to get 1194 kB of archives.
2015-09-14 14:23:01 INFO install After this operation, 9216 B disk space will be freed.
2015-09-14 14:23:01 INFO install WARNING: The following packages cannot be authenticated!
2015-09-14 14:23:01 INFO install dnsutils bind9-host libisc95 libdns100 libisccc90 libisccfg90 liblwres90
2015-09-14 14:23:01 INFO install libbind9-90
2015-09-14 14:23:01 INFO install E: There are problems and -y was used without --force-yes
2015-09-14 14:23:01 INFO worker.uniter.jujuc server.go:158 running hook tool "juju-log" ["Couldn't acquire DPKG lock. Will retry in 10 seconds."]
2015-09-14 14:23:01 DEBUG worker.uniter.jujuc server.go:159 hook context id "contrail-webui/0-install-414841784440951436"; dir "/var/lib/juju/agents/unit-contrail-webui-0/charm"
2015-09-14 14:23:01 INFO juju-log Couldn't acquire DPKG lock. Will retry in 10 seconds.
2015-09-14 14:23:11 INFO install Reading package lists...
2015-09-14 14:23:11 INFO install Building dependency tree...
2015-09-14 14:23:11 INFO install Reading state information...
2015-09-14 14:23:11 INFO install The following packages were automatically installed and are no longer required:
2015-09-14 14:23:11 INFO install libfreetype6 os-prober
2015-09-14 14:23:11 INFO install Use 'apt-get autoremove' to remove them.
2015-09-14 14:23:11 INFO install The following packages will be upgraded:
2015-09-14 14:23:11 INFO install bind9-host dnsutils libbind9-90 libdns100 libisc95 libisccc90 libisccfg90
2015-09-14 14:23:11 INFO install liblwres90
2015-09-14 14:23:11 INFO install 8 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2015-09-14 14:23:11 INFO install Need to get 1194 kB of archives.
2015-09-14 14:23:11 INFO install After this operation, 9216 B disk space will be freed.
2015-09-14 14:23:11 INFO install WARNING: The following packages cannot be authenticated!
2015-09-14 14:23:11 INFO install dnsutils bind9-host libisc95 libdns100 libisccc90 libisccfg90 liblwres90
2015-09-14 14:23:11 INFO install libbind9-90
2015-09-14 14:23:11 INFO install E: There are problems and -y was used without --force-yes
2015-09-14 14:23:11 INFO install Traceback (most recent call last):
2015-09-14 14:23:11 INFO install File "/var/lib/juju/agents/unit-contrail-webui-0/charm/hooks/install", line 24, in <module>
2015-09-14 14:23:11 INFO install install()
2015-09-14 14:23:11 INFO install File "/var/lib/juju/agents/unit-contrail-webui-0/charm/hooks/install", line 19, in install
2015-09-14 14:23:11 INFO install apt_upgrade(fatal=True, dist=True)
2015-09-14 14:23:11 INFO install File "/var/lib/juju/agents/unit-contrail-webui-0/charm/hooks/charmhelpers/fetch/__init__.py", line 206, in apt_upgrade
2015-09-14 14:23:11 INFO install _run_apt_command(cmd, fatal)
2015-09-14 14:23:11 INFO install File "/var/lib/juju/agents/unit-contrail-webui-0/charm/hooks/charmhelpers/fetch/__init__.py", line 445, in _run_apt_command
2015-09-14 14:23:11 INFO install result = subprocess.check_call(cmd, env=env)
2015-09-14 14:23:11 INFO install File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
2015-09-14 14:23:11 INFO install raise CalledProcessError(retcode, cmd)
2015-09-14 14:23:11 INFO install subprocess.CalledProcessError: Command '['apt-get', '--assume-yes', '--option=Dpkg::Options::=--force-confold', 'dist-upgrade']' returned non-zero exit status 100
2015-09-14 14:23:11 INFO juju.worker.uniter.context context.go:543 handling reboot
2015-09-14 14:23:11 ERROR juju.worker.uniter.operation runhook.go:103 hook "install" failed: exit status 1
2015-09-14 14:23:11 DEBUG juju.worker.uniter modes.go:31 [AGENT-STATUS] failed: run install hook
2015-09-14 14:23:12 INFO juju.worker.uniter modes.go:543 ModeContinue exiting
2015-09-14 14:23:12 INFO juju.worker.uniter modes.go:541 ModeHookError starting
2015-09-14 14:23:12 DEBUG juju.worker.uniter.filter filter.go:597 want resolved event
2015-09-14 14:23:12 DEBUG juju.worker.uniter.filter filter.go:591 want forced upgrade true
2015-09-14 14:23:12 DEBUG juju.worker.uniter.filter filter.go:727 no new charm event
2015-09-14 14:23:12 DEBUG juju.worker.uniter modes.go:31 [AGENT-STATUS] error: hook failed: "install"
2015-09-14 14:23:28 DEBUG juju.worker.leadership tracker.go:138 contrail-webui/0 renewing lease for contrail-webui leadership
2015-09-14 14:23:28 DEBUG juju.worker.leadership tracker.go:165 checking contrail-webui/0 for contrail-webui leadership
2015-09-14 14:23:29 DEBUG juju.worker.leadership tracker.go:180 contrail-webui/0 confirmed for contrail-webui leadership until 2015-09-14 14:24:28.148361545 +0000 UTC