The Trailhead calls out that "Authentication providers like Facebook frequently change authentication requirements to increase security." This one is out of date, but would be very helpful if updated!

Module3RegistrationHandler Lines 160-161 read as follows:

160 u.languagelocalekey = UserInfo.getLocale();
161 u.localesidkey = UserInfo.getLocale();

In fact, the first line should be using UserInfo.getLanguage() and not getLocale.

As currently written, this produces an error when a user registers - en_AU is not a valid Language value for the restricted picklist. Changing the code to getLanguage resolves the problem.

Method ( Userinfo.getLocal() ) assigned to populate u.languagelocalekey field while creating a user record is incorrect as it doesn't return the expected picklist value for Language field
Acceptable values are available [here]((https://help.salesforce.com/articleView?id=000327115&language=en_US&type=1&mode=1)