is install script broken?
I tried few weeks ago, and was getting stuck at error abound mysql root password.
Today I tried again from scrach. Tried Debian 8, Debian 9, Ubuntu 16.04
are you sure, that you enter the same password?
By the way sometimes it happen if you use special symbols in you MySQL password. Try to use MySQL password without special symbols like: !@#$%^&*<>
I am sure, password is simple only lower case letters and numbers. no special characters. And password is correct tried around 20 times. password works in terminal, but not in installer.