Djblets provides a RegistrationForm for helping register new users,

taking in a username, password, full name, and e-mail address. The code

for doing this is a bit old, wasn't unit tested, and had some warts.
There's improvements now in the documentation and coding style, bringing

it up to modern standards. The biggest changes, though, are in the

saving logic. We previously created the object in the parent database

transaction, and if there was a conflict, we'd try to fetch an existing

user to confirm and then provide an error to the user on the form.
The problem with this is that we'd break the transaction by way of

the constraint error, and then we'd try to look up the other user in the

same transaction. This didn't always work, and was a dangerous way of

doing it. Instead, we needed to ensure we were creating the object in

its own transaction, using transaction.atomic(). This is the same

approach used by methods like Model.objects.get_or_create().
We also no longer fetch an entire User when checking for duplicates.

We just check if a row exists in the database. This speeds things up a

bit.
Unit tests have been added for all of RegistrationForm's

functionality.

Unit tests pass on all supported versions of Django and Python.