Previously this file was agnostic to USERNAME_FIELD being email, would it be acceptable to continue that?

This is kind of ugly, but maybe it would be along these lines.  I'm willing to be talked about of this.

```python
PasswordResetForm = type('PasswordResetForm', (forms.BaseForm,), {User.USERNAME_FIELD...}
```

Actually on second thought, you can't reset a password without an email.  NEVERMIND.