from django.utils.encoding import python_2_unicode_compatible
from django.utils.translation import ugettext_lazy as _
from django.contrib.gis.db import models


@python_2_unicode_compatible
class GeoRegion(models.Model):
    name = models.CharField(_('Name'), max_length=255)
    slug = models.SlugField(_('Slug'), max_length=255)

    kind = models.CharField(_('Kind of Region'), max_length=255,
        choices=(
            ('country', _('country')),
            ('state', _('state')),
            ('admin_district', _('administrative district')),
            ('district', _('district')),
            ('admin_cooperation', _('administrative cooperation')),
            ('municipality', _('municipality')),
            ('borough', _('borough')),
            ('zipcode', _('zipcode')),
        )
    )
    kind_detail = models.CharField(max_length=255, blank=True)
    level = models.IntegerField(default=0)
    region_identifier = models.CharField(max_length=255, blank=True)
    global_identifier = models.CharField(max_length=255, blank=True)

    area = models.FloatField(_('Area'), default=0.0)  # in Sqm
    population = models.IntegerField(null=True, blank=True)
    valid_on = models.DateTimeField(null=True, blank=True)

    geom = models.MultiPolygonField(_('geometry'), geography=True)
    gov_seat = models.PointField(_('geometry'), null=True, geography=True)

    part_of = models.ForeignKey('self', verbose_name=_('Part of'), null=True,
        on_delete=models.SET_NULL
    )

    objects = models.GeoManager()

    class Meta:
        verbose_name = _('Geo Region')
        verbose_name_plural = _('Geo Regions')

    def __str__(self):
        return '%s (%s)' % (self.name, self.pk)

from django.utils.encoding import python_2_unicode_compatible
from django.utils.translation import ugettext_lazy as _
from django.contrib.gis.db import models


@python_2_unicode_compatible
class GeoRegion(models.Model):
    name = models.CharField(_('Name'), max_length=255)
    slug = models.SlugField(_('Slug'), max_length=255)

    kind = models.CharField(_('Kind of Region'), max_length=255,
        choices=(
            ('country', _('country')),
            ('state', _('state')),
            ('admin_district', _('administrative district')),
            ('district', _('district')),
            ('admin_cooperation', _('administrative cooperation')),
            ('municipality', _('municipality')),
            ('borough', _('borough')),
            ('zipcode', _('zipcode')),
        )
    )
    kind_detail = models.CharField(max_length=255, blank=True)
    level = models.IntegerField(default=0)
    region_identifier = models.CharField(max_length=255, blank=True)
    global_identifier = models.CharField(max_length=255, blank=True)

    area = models.FloatField(_('Area'), default=0.0)  # in Sqm
    population = models.IntegerField(null=True, blank=True)
    valid_on = models.DateTimeField(null=True, blank=True)

    geom = models.MultiPolygonField(_('geometry'), geography=True)
    gov_seat = models.PointField(_('geometry'), null=True, geography=True)

    part_of = models.ForeignKey('self', verbose_name=_('Part of'), null=True,
        on_delete=models.SET_NULL
    )

    class Meta:
        verbose_name = _('Geo Region')
        verbose_name_plural = _('Geo Regions')

    def __str__(self):
        return '%s (%s)' % (self.name, self.pk)

Remove geomanager from GeoRegion