Misago/misago/core/validators.py

from django.core.exceptions import ValidationError
from django.utils.translation import ugettext_lazy as _
from misago.core.utils import slugify


class validate_sluggable(object):
    def __init__(self, error_short=None, error_long=None):
        self.error_short = error_short or _(
            "Value has to contain alpha-numerical characters.")
        self.error_long = error_long or _("Value is too long.")

    def __call__(self, value):
        slug = slugify(value)

        if not slug.replace('-', ''):
            raise ValidationError(self.error_short)

        if len(slug) > 255:
            raise ValidationError(self.error_long)