# -*- coding: utf-8 -*-
from autoslug import AutoSlugField
try:
    from django.urls import reverse
except ImportError:  # For Django 1.8 (EOL "until April 2018")
    from django.core.urlresolvers import reverse
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
from django.utils.translation import ugettext as _
from model_utils import Choices
from mptt.managers import TreeManager
from mptt.models import MPTTModel, TreeForeignKey


class JednostkaAdministracyjnaManager(TreeManager):

    def with_category(self):
        return self.select_related('category')


class JednostkaAdministracyjnaQuerySet(models.QuerySet):

    def voivodeship(self):
        return self.filter(category__level=1)

    def county(self):
        return self.filter(category__level=2)

    def community(self):
        return self.filter(category__level=3)

    def area(self, jst):
        return self.filter(tree_id=jst.tree_id,
                           lft__range=(jst.lft, jst.rght))


@python_2_unicode_compatible
class Category(models.Model):
    LEVEL = Choices((1, 'voivodeship', _('voivodeship')),
                    (2, 'county', _('county')),
                    (3, 'community', _('community')))
    name = models.CharField(max_length=50)
    slug = AutoSlugField(populate_from='name')
    level = models.IntegerField(choices=LEVEL, db_index=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = _('Category')
        verbose_name_plural = _('Categories')


@python_2_unicode_compatible
class JednostkaAdministracyjna(MPTTModel):
    id = models.CharField(max_length=7, primary_key=True)
    parent = TreeForeignKey('self', null=True, blank=True,
                            related_name='children',
                            on_delete=models.CASCADE)
    name = models.CharField(_('Name'), max_length=36)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    slug = AutoSlugField(populate_from='name', unique=True)
    updated_on = models.DateField(verbose_name=_("Updated date"))
    active = models.BooleanField(default=False)
    objects = JednostkaAdministracyjnaManager.from_queryset(JednostkaAdministracyjnaQuerySet)()

    def __str__(self):
        return u'{0}'.format(self.name)

    def get_absolute_url(self):
        return reverse('teryt:details', kwargs={'slug': self.slug})

    class MPTTMeta:
        order_insertion_by = ['name']

    class Meta:
        verbose_name = _('Unit of administrative division')
        verbose_name_plural = _('Units of administrative division')


@python_2_unicode_compatible
class SIMC(models.Model):
    id = models.CharField(max_length=7, primary_key=True)
    sym_pod = models.ForeignKey('self', blank=True, on_delete=models.CASCADE)
    terc = models.ForeignKey(JednostkaAdministracyjna, on_delete=models.CASCADE)
    name = models.CharField(max_length=100)
    updated_on = models.DateField(verbose_name=_("Updated date"))

    def __str__(self):
        return "{}".format(self.name)
@@ -341,16 +341,21 @@
 ugettext
+_lazy
  as _%0Afr

Use ugettext_lazy in models.py