Comment 58 for bug 1579712

It took quite some time for me to find this solution. When the average user starts googling this, they are going to find all sorts of things which do not apply, for example:

http://itsfoss.com/fix-update-errors-ubuntu-1404/
https://askubuntu.com/questions/615203/software-updates-stuck-downloading-after-15-04-upgrade

What a nightmare! This demonstrates why the system update utility needs to include a twitter-type client to inform the user of emerging issues related to broken update functionality. How else will the average user cope with a new issue like this, when there are so many possible causes for the same type of problem?

Yes I know, it poses the question of who should have the authority to broadcast alerts. Perhaps a majority vote by a jury of lead developers or team managers who could activate the feature by signing a proposed broadcast message with their PGP key. Moderators of the forum or the bug tracker would then submit proposals for broadcast messages to a mailing list that goes to the jury. This would eliminate the possibility of using the broadcast system for spam.

In any case, the manual fix in the description is not sufficiently clear: many people who are capable of typing terminal commands will not know to replace 'amd64' with 'i386' or whatever is appropriate. A script which automates this might be a better solution.
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@neil.mayhew

> I'm not sure what happens if someone is using Synaptic or Gnome Software. I assume it would be necessary to use System Monitor to kill off appstreamcli.

@olliniem

> forever inactive window with no possibility to interfere

Best quick recovery method is to launch 'top' in terminal & kill that process ID. It does affect Software Center, Software Updater, adding PPA's, et cetera.