django with sqlite unable to open database file

I have sqlite database setting like in my production server :

DATABASES = {
'default': {
    'ENGINE': 'django.db.backends.sqlite3',
    'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
}

}

I have also tried chown www-data path_to_db and chmod 777 path_to_db but its still showing error saying unable to open database.. whats the issue here