我在deepin中运行sudo apt update命令时出现下面错误：
[sudo] password for ********:
Hit:1 http://packages.deepin.com/deepin panda InRelease
Get:2 http://repository.spotify.com stable InRelease [3,302 B]
Err:2 http://repository.spotify.com stable InRelease                                                        
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A87FF9DF48BF1C90
Reading package lists... Done                                                                              
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.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

请问怎么解决？ @aida