Django Apscheduler: Error getting due jobs from job store 'default': connection already closed

I have configured django-apscheduler in my django project. I am getting error of gettig due job store. I used these configuration in my settings.py file.

SCHEDULER_CONFIG = {
    "apscheduler.jobstores.default": {
        "class": "django_apscheduler.jobstores:DjangoJobStore"
    },
    'apscheduler.executors.processpool': {
        "type": "threadpool"
    }
}
SCHEDULER_AUTOSTART = True

Also I have created a scheduler.py file parallel to settings.py with these code lines.

import logging

from apscheduler.schedulers.background import BackgroundScheduler
from django.conf import settings

scheduler = BackgroundScheduler(settings.SCHEDULER_CONFIG,job_defaults={'misfire_grace_time': 15*60},deamon=True)


def createJob(func, params, tz, id, hour='*', minute='*', ):
    scheduler.add_job(func, 'cron', params, hour=hour, minute=minute, timezone=tz, id=id)


def printJob():
    try:
        scheduler.print_jobs()
    except Exception as e:
        pass


def removeJob(id):
    try:
        scheduler.remove_job(id)
    except Exception as e:
        pass


def start():
    if settings.DEBUG:
        logging.basicConfig()
        logging.getLogger('apscheduler').setLevel(logging.DEBUG)

    scheduler.start()


start()