Fixed #4833 -- Validate email addresses with localhost as domain

        raise ValidationError('')

class EmailValidator(RegexValidator):

class EmailValidator(object):

    message = _('Enter a valid e-mail address.')

    code = 'invalid'

    user_regex = re.compile(

        r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*$"  # dot-atom

        r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-\011\013\014\016-\177])*"$)', # quoted-string

        re.IGNORECASE)

    domain_regex = re.compile(

        r'(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?$)'  # domain

        # literal form, ipv4 address (SMTP 4.1.3)

        r'|^\[(25[0-5]|2[0-4]\d|[0-1]?\d?\d)(\.(25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}\]$',

        re.IGNORECASE)

    domain_whitelist = ['localhost']

    def __init__(self, message=None, code=None, whitelist=None):

        if message is not None:

            self.message = message

        if code is not None:

            self.code = code

        if whitelist is not None:

            self.domain_whitelist = whitelist

    def __call__(self, value):

        value = force_text(value)

        if not value or '@' not in value:

            raise ValidationError(self.message, code=self.code)

        user_part, domain_part = value.split('@', 1)

        if not self.user_regex.match(user_part):

            raise ValidationError(self.message, code=self.code)

        if (not domain_part in self.domain_whitelist and

                not self.domain_regex.match(domain_part)):

            # Try for possible IDN domain-part

            try:

            super(EmailValidator, self).__call__(value)

        except ValidationError as e:

            # Trivial case failed. Try for possible IDN domain-part

            if value and '@' in value:

                parts = value.split('@')

                try:

                    parts[-1] = parts[-1].encode('idna').decode('ascii')

                except UnicodeError:

                    raise e

                super(EmailValidator, self).__call__('@'.join(parts))

                domain_part = domain_part.encode('idna').decode('ascii')

                if not self.domain_regex.match(domain_part):

                    raise ValidationError(self.message, code=self.code)

                else:

                raise

                    return

            except UnicodeError:

                pass

            raise ValidationError(self.message, code=self.code)

email_re = re.compile(

    r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*"  # dot-atom

    # quoted-string, see also http://tools.ietf.org/html/rfc2822#section-3.2.5

    r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-\011\013\014\016-\177])*"'

    r')@((?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)$)'  # domain

    r'|\[(25[0-5]|2[0-4]\d|[0-1]?\d?\d)(\.(25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}\]$', re.IGNORECASE)  # literal form, ipv4 address (SMTP 4.1.3)

validate_email = EmailValidator(email_re, _('Enter a valid email address.'), 'invalid')

validate_email = EmailValidator()

slug_re = re.compile(r'^[-a-zA-Z0-9_]+$')

validate_slug = RegexValidator(slug_re, _("Enter a valid 'slug' consisting of letters, numbers, underscores or hyphens."), 'invalid')

------------------

.. data:: validate_email

    A :class:`RegexValidator` instance that ensures a value looks like an

    An ``EmailValidator`` instance that ensures a value looks like an

    email address.

``validate_slug``

    (validate_email, 'example@valid-----hyphens.com', None),

    (validate_email, 'example@valid-with-hyphens.com', None),

    (validate_email, 'test@domain.with.idn.tld.उदाहरण.परीक्षा', None),

    (validate_email, 'email@localhost', None),

    (EmailValidator(whitelist=['localdomain']), 'email@localdomain', None),

    (validate_email, None, ValidationError),

    (validate_email, '', ValidationError),