Clean up defunct celery PeriodicTask entries

gistfile1.py

from djcelery.models import PeriodicTask
from django.utils import importlib

bad_tasks = []
good_tasks = []

for pt in PeriodicTask.objects.iterator():
    path_name, task_name = pt.task.rsplit('.', 1)
    try:
        module = importlib.import_module(path_name)
    except ImportError:
        bad_tasks.append(pt)
        continue
    if not hasattr(module, task_name):
        bad_tasks.append(pt)
        continue
    good_tasks.append(pt)

##########
Review bad_tasks before proceeding:
##########

for t in bad_tasks:
   t.delete()