Consistent regex for django.contrib.auth.forms.AuthenticationForm
|Reported by:||Owned by:||nobody|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
In django/contrib/auth/forms.py, two out of three forms validate the username with a regex (UserCreationForm, UserChangeForm), but the third (AuthenticationForm) does not.
This patch copies the same regex to apply in that form too.