ttf-mscorefonts-installer is showing up in Update Manager as having been downloaded but not installed. When I run
sudo apt-get remove ttf-mscorefonts-installer I get the message
dpkg: warning: there's no installed package matching ttf-mscorefonts-installer:amd64
I can't uncheck the box next to ttf-mscorefonts-installer in the Update Manager interface, and I can't install any other updates because I get the error message
Requires installation of untrusted packages
The action would require the installation of packages from not authenticated sources.
How do I get rid of
ttf-mscorefonts-installer so that it stops causing problems?