It claims that there has to be at least 8 characters, 1 upper case, 1 lowercase, 1 number, and 1 special character. But from the regex they use to check, special characters are

!@#$%^&*

. And if you include any characters are that not in that list, the password fails the check. I misread the regex, and it does let you include any other non-whitespace characters. But it doesn't allow spaces. And it used to. And you can set a password with a space at install...