Case:”W: GPG error: http://ftp.debian.org jessie-backports”(Openning)

Case: Reading package lists… Done W: GPG error: http://ftp.debian.org jessie-backports InRelease: Could not execute ‘gpgv’ to verify signature (is gpgv installed?) W: GPG error: http://mirrordirector.raspbian.org jessie InRelease: Could not execute ‘gpgv’ to verify signature (is gpgv installed?)