I would like to disable password login for a user. But instead of the error message (Public key) I would not like the user notice that the password login is disabled and prompting him for password.

So far I know I can disable password login for all users except one with

PasswordAuthentication no
Match User toto
PasswordAuthentication yes

But attempting to login as 'not_toto' will result an error message from the server, which I do not wish.

Do I need to modify openssh sources to do that? Or is there a configuration option which can do the job?

Edit:

Having two ssh servers running is an option, so killing connections with iptables or via another method (outside ssh configuration) could do it.

Edit 2:

I want to do this as I need two ssh instances, one in the official door to get in and the other is a honeypot. So the bots will give their password but never letting them in. (nb: this is a personal project I am the only one using the server and not logging colleagues passwords nor other nasty things, I just want to make some stats on bots)

The first ssh server (say official) is OpenSSH_7.4p1 Debian-10+deb9u1, OpenSSL 1.0.2l 25 May 2017, installed with Debian packages.

The 'honeypot' is a modified version of Openssh-7.4p1 that logs username and passwords from login attempts. Actually PAM should be enabled on this one but I will double check it. Maybe your option symcbean may be the right one.