gpg: failed to start the dirmngr ‘/usr/bin/dirmngr’: No such file or directory

Al querer agregar un repositorio aparece el error:

gpg: failed to start the dirmngr '/usr/bin/dirmngr': No such file or directory

Acompañado de:

gpg: connecting dirmngr at '/tmp/tmpyq7kwe2x/S.dirmngr' failed: No such file or directory
gpg: keyserver receive failed: No dirmngr

Para solucionarlo hay que instalar el paquete dirmgr:

sudo apt-get install dirmngr

y listo.