Failed to fetch updates messsage

Question

I get a failed to fetch updates message when I open the App centre. Below are the details displayed in the details dropdown. No big deal but annoying

W: GPG error: http://repository.spotify.com stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A87FF9DF48BF1C90 E: The repository 'http://repository.spotify.com stable InRelease' is not signed. W: Updating from such a repository can't be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. E: http://repository.spotify.com stable InRelease is not (yet) available (The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A87FF9DF48BF1C90)

Answer 1

Looks like Spotify's repository signing key is missing on your system. To install it, execute

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 931FF8E79F0876134EDDBDCCA87FF9DF48BF1C90

(as written here in 'Debian package' section).