Comment 40 for bug 1522675

I have similar problem with flashplugin-installer and ttf-mscorefonts-installer packages:

flashplugin-installer: processing...
flashplugin-installer: downloading http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_20161026.1.orig.tar.gz
Get:1 http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_20161026.1.orig.tar.gz [27,2 MB]
Fetched 27,2 MB in 25s (1.085 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/adobe-flashplugin_20161026.1.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_20161026.1.orig.tar.gz
Flash Plugin installed.
ttf-mscorefonts-installer: processing...
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/andale32.exe
Get:1 http://downloads.sourceforge.net/corefonts/andale32.exe [198 kB]
Fetched 198 kB in 2s (96,3 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/andale32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/arial32.exe
Get:1 http://downloads.sourceforge.net/corefonts/arial32.exe [554 kB]
Fetched 554 kB in 2s (248 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/arial32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/arialb32.exe
Get:1 http://downloads.sourceforge.net/corefonts/arialb32.exe [168 kB]
Fetched 168 kB in 2s (71,9 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/arialb32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/comic32.exe
Get:1 http://downloads.sourceforge.net/corefonts/comic32.exe [246 kB]
Fetched 246 kB in 2s (95,3 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/comic32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/courie32.exe
Get:1 http://downloads.sourceforge.net/corefonts/courie32.exe [646 kB]
Fetched 646 kB in 2s (273 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/courie32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/georgi32.exe
Get:1 http://downloads.sourceforge.net/corefonts/georgi32.exe [392 kB]
Fetched 392 kB in 1s (233 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/georgi32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/impact32.exe
Get:1 http://downloads.sourceforge.net/corefonts/impact32.exe [173 kB]
Fetched 173 kB in 1s (125 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/impact32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/times32.exe
Get:1 http://downloads.sourceforge.net/corefonts/times32.exe [662 kB]
Fetched 662 kB in 2s (314 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/times32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/trebuc32.exe
Get:1 http://downloads.sourceforge.net/corefonts/trebuc32.exe [357 kB]
Fetched 357 kB in 1s (212 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/trebuc32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/verdan32.exe
Get:1 http://downloads.sourceforge.net/corefonts/verdan32.exe [352 kB]
Fetched 352 kB in 1s (248 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/verdan32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/webdin32.exe
Get:1 http://downloads.sourceforge.net/corefonts/webdin32.exe [185 kB]
Fetched 185 kB in 1s (137 kB/s)
W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/webdin32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)

File permissions:

# find /var/lib/update-notifier/package-data-downloads/ -ls
  9052762 4 drwxr-xr-x 3 root root 4096 nov 4 10:30 /var/lib/update-notifier/package-data-downloads/
  9047630 0 -rw-r--r-- 1 root root 0 nov 4 10:30 /var/lib/update-notifier/package-data-downloads/flashplugin-installer
  9078917 0 -rw-r--r-- 1 root root 0 nov 4 10:27 /var/lib/update-notifier/package-data-downloads/ttf-mscorefonts-installer
  9052766 4 drwxr-xr-x 2 root root 4096 nov 4 10:30 /var/lib/update-notifier/package-data-downloads/partial