celery_config.py

from celery import Celery
from celery.schedules import crontab
from pyramid_mailer.message import Message
from intranet_backend_api.celery_bundle.celery_settings import mailer
# Define app
app = Celery()
## Broker settings.
broker_url = 'amqp://app_rmq:pass@localhost:5672/intranet'
# Set timezone, for DST
timezone = 'Europe/London'

# Modules to import when the Celery worker starts.
imports = ('intranet_backend_api.celery_bundle.tasks.time_attendance')

## Using the database to store task state and results.
#result_backend = 'db+sqlite:///results.db'


def my_on_failure(self, exc, task_id, args, kwargs, einfo):
    message_formatted = 'Oh no! Task failed: {0!r}'.format(exc)
    message = Message(
                subject="Failed celery task",
                sender='admin@example.com',
                recipients=['luke@example.com'],
                body=message_formatted)
    mailer.send_immediately(message)

task_annotations = {'*': {'on_failure': my_on_failure}}

app.conf.beat_schedule = {
    'users-not-clocked-in': {
        'task': 'intranet_backend_api.celery_bundle.tasks.time_attendance.not_clocked_in',
        'schedule': crontab(hour=11, minute=40, day_of_week="mon-fri")
    },
}

time_attendance.py

@app.task
def users_not_clocked_in():
    message = Message(
        subject="Users not clocked in",
        sender='admin@example.com',
        recipients=['luke@example.com'],
        html="something",
        body=None)
    mailer.send_immediately(message)