Running sudo pkexec /usr/lib/update-notifier/package-data-downloader
I received the following error (links obfuscated due to ask policy):
flashplugin-installer: processing...
flashplugin-installer: downloading _http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_20161213.1.orig.tar.gz
Err:1 _http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_20161213.1.orig.tar.gz
Could not open file /var/lib/update-notifier/package-data-downloads/partial/adobe-flashplugin_20161213.1.orig.tar.gz - open (2: No such file or directory) [IP: 91.189.92.191 80]
E: Failed to fetch _http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_20161213.1.orig.tar.gz Could not open file /var/lib/update-notifier/package-data-downloads/partial/adobe-flashplugin_20161213.1.orig.tar.gz - open (2: No such file or directory) [IP: 91.189.92.191 80]
E: Download Failed
I manually downloaded the file from the URL specified, created a new 'partial' directory in /var/lib/update-notifier/package-data-downloads
, moved the download to there and then ran the sudo pkexec /usr/lib/update-notifier/package-data-downloader
command again. Which I think appeared to work (Ubuntu 16.04)