django - Can't save object using save() - AttributeError: 'DatabaseWrapper' object has no attribute 'Database' -

i have class , i'm trying create object using shell:

class task(models.model):     person = models.onetoonefield(person)     start_date = models.datefield(null=true)     end_date = models.datefield(null=true)     free_day = models.datefield(null=true)     text = models.charfield(max_length=100)      def __str__(self):         return '%s' % self.person 

p = person.objects.get(username='herehere') t = task(person=p,text='blabla') t.save() 

but got error:

attributeerror: 'databasewrapper' object has no attribute 'database' 

if change

person = models.onetoonefield(person) 

to

person = models.onetoonefield(person, primary_key) 

i got

'databasewrapper' object has no attribute 'operators' 

my settings.py db configurations:

databases = {     'default': {         'engine': 'django.db.backends.sqlite3',         'name': os.path.join(base_dir, 'db.sqlite3'),     },     'ldap': {         'engine': 'ldapdb.backends.ldap',         'name': auth_ldap_server_uri,         'user': auth_ldap_bind_dn,         'password': auth_ldap_bind_password,     }, }