def METHOD_NAME(self):
    email = self.cleaned_data['email'].lower()
    # error if there is already an account (User, Person) associated with this email
    try:
        user = User.objects.get(username__iexact=email)
        person = Person.objects.get(user=user)
        if user and person:
            raise forms.ValidationError("This account already exists. [name=%s, id=%s, email=%s]" % (person.name,person.id,email))
    except ObjectDoesNotExist:
        pass
    # error if email already exists
    if Email.objects.filter(address=email,active=True):
        raise forms.ValidationError("This email address already exists in the database")
    return email