flashplugin-installer: Can't drop priviledges for downloading as file Warning

[Carroarmato0]

flashplugin-installer: downloading http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_20160616.1.orig.tar.gz
Get:1 http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_20160616.1.orig.tar.gz [27,1 MB]
Fetched 27,1 MB in 8s (3.125 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/adobe-flashplugin_20160616.1.orig.tar.gz' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
Installing from local file /var/lib/update-notifier/package-data-downloads/partial/adobe-flashplugin_20160616.1.orig.tar.gz
Flash Plugin installed.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: flashplugin-installer 11.2.202.626ubuntu0.16.04.1
ProcVersionSignature: Ubuntu 4.4.0-24.43-generic 4.4.10
Uname: Linux 4.4.0-24-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Fri Jun 17 09:50:33 2016
InstallationDate: Installed on 2016-04-26 (51 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: flashplugin-nonfree
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[tt8811 (tt8811)]

This is still appearing -- saw it again this morning.

[dino99 (9d9)]

This is not a "flashplugin" issue as it happens randomly with some other packages when a script validate an upgrade. that one has not been updated to support the new apt design "'_apt'"

The real problem is : there is _apt user on the system

grep -B2 _apt /var/lib/dpkg/info/apt.postinst

 # add unprivileged user for the apt methods
 adduser --force-badname --system --home /nonexistent \
     --no-create-home --quiet _apt || true

 # Fixup any mistake in the home directory of the _apt user
 if dpkg --compare-versions "$2" lt-nl 1.1~exp10~; then
     usermod --home /nonexistent _apt

[David Burrows (snadge)]

I just got this on a new 16.04.3 install. Flash version 28.0.0.161. I tried reinstalling it after the above workaround (theres a fi missing at the end). It still prints the error message, but the new version of flash appears to be installed and working anyway. This bug is a bit stale now.