Django crispy is bow using a filter rather than a tag.
Using the `crispy` tag resulted in two imbricated forms being
generated, and a broken "send" button.
At the moment, the email is stored in the `username` field.
Django form-handling looks for the default email
field [0] to find the user email.
If it doesnet find anything, it fails silently
(to avoid leaking information about the users
present in the system, which is a good thing)
The fix was to change the field used to check for the email.
[0] eea4f92f9a/django/contrib/auth/forms.py (L326-L337)
