I agree that it seems to miss an argument in the call from deploy-server-cert.
I have compared the versions up to the much more recent 3.5.2-1 but the situation is the same.
Reproducing this doesn't need a lot of pre-setup:
$ apt install postfix ssl-cert
$ postfix tls deploy-server-cert /etc/ssl/certs/ssl-cert-snakeoil.pem /etc/ssl/private/ssl-cert-snakeoil.key
I agree that it seems to miss an argument in the call from deploy-server-cert.
I have compared the versions up to the much more recent 3.5.2-1 but the situation is the same.
Reproducing this doesn't need a lot of pre-setup: certs/ssl- cert-snakeoil. pem /etc/ssl/ private/ ssl-cert- snakeoil. key
$ apt install postfix ssl-cert
$ postfix tls deploy-server-cert /etc/ssl/