Simple E-mail registration

# in forms.py
from django import forms
from django.utils.translation import ugettext_lazy as _
from django.utils.http import int_to_base36
from django.contrib.auth.models import User
from django.contrib.auth.tokens import default_token_generator
from django.contrib.sites.models import Site

class RegistrationForm(forms.ModelForm):
    username = forms.RegexField(label=_("Username"), max_length=30, regex=r'^\w+$',
        help_text = _("Required. 30 characters or fewer. Alphanumeric characters only (letters, digits and underscores)."),
        error_message = _("This value must contain only letters, numbers and underscores."))
    email = forms.EmailField(label=_("E-mail"), max_length=75)

    class Meta:
        model = User
        fields = ("username",)

    def clean_username(self):
        username = self.cleaned_data["username"]
        try:
            User.objects.get(username=username)
        except User.DoesNotExist:
            return username
        raise forms.ValidationError(_("A user with that username already exists."))

    def clean_email(self):
        """
        Validate that the supplied email address is unique for the
        site.
        """
        
        if User.objects.filter(email__iexact=self.cleaned_data['email']).count():
            raise forms.ValidationError(_(u'This email address is already in use. Please supply a different email address.'))
        return self.cleaned_data['email']

    def save(self, commit=True, domain_override=None, email_template_name='registration/password_reset_email.html',
             use_https=False, token_generator=default_token_generator):
        user = super(RegistrationForm, self).save(commit=False)
        user.set_unusable_password()
        if not commit:
            return user
        user.save()

        from django.core.mail import send_mail
        if not domain_override:
            current_site = Site.objects.get_current()
            site_name = current_site.name
            domain = current_site.domain
        else:
            site_name = domain = domain_override
        t = loader.get_template(email_template_name)
        c = {
            'email': user.email,
            'domain': domain,
            'site_name': site_name,
            'uid': int_to_base36(user.id),
            'user': user,
            'token': token_generator.make_token(user),
            'protocol': use_https and 'https' or 'http',
        }
        send_mail(_("Password reset on %s") % site_name,
            t.render(Context(c)), None, [user.email], fail_silently=False)
        return user


# in views.py
from django.core.urlresolvers import reverse
from django.shortcuts import render_to_response
from django.template import RequestContext
from django.http import HttpResponseRedirect
from django.contrib.auth.tokens import default_token_generator
from django.contrib.sites.models import Site

def register(request, template_name='registration/registration_form.html', 
        email_template_name='registration/password_reset_email.html', token_generator=default_token_generator):
    if request.method == 'POST':
        form = RegistrationForm(data=request.POST)
        if form.is_valid():
            opts = {}
            opts['use_https'] = request.is_secure()
            opts['token_generator'] = token_generator
            opts['email_template_name'] = email_template_name
            if not Site._meta.installed:
                opts['domain_override'] = RequestSite(request).domain
            form.save(**opts)
            return HttpResponseRedirect(reverse('registration_complete'))
    else:
        form = RegistrationForm()
    
    return render_to_response(template_name,
                              {'form': form},
                              RequestContext(request))