SQL 2012 :: Contained Users Password Hash

I would like to perform an audit of weak passwords, which is well documented for sql users. Using the same methodology, I should be able to audit weak passwords for contained users. To accomplish this, I must be able to find the location of the password hashes for the contained users.

I have looked at sys.syslogins and sys.sql_logins, which both have the password hash for server level users, but not contained users. I was able to find sys.sysusers, which does contain contained users, but no password hash.

What is the location of the password hashes for contained users?