Fixed python 3 support. Refs #17320

from __future__ import unicode_literals

import string

from django.db import models

    checks = ((s in value) for s in string.whitespace)

    if any(checks):

        raise ValidationError(

            _(u"The domain name cannot contain any spaces or tabs."))

            _("The domain name cannot contain any spaces or tabs."))

class SiteManager(models.Manager):