Release1.5.4

I suggest to change the error message for failed MySQL connects in all relevant modules to 

module.fail_json(msg="unable to connect. Check login_user and login_password are correct (alternatively if ~/.my.cnf contains correct credential) and the path to the Unix domain socket (use parameter login_unix_socket if not in default path).")

or something along that line. That makes it clearer that it is not necessarily the credentials which are wrong, but could also be the unix socket. See issue 6860.