Sentry broken when using CELERY_WORKER_MAX_TASKS_PER_CHILD = 1

[massover]

https://docs.sentry.io/clients/python/transports/#sync
getsentry/raven-python#881

Raven does not send exceptions/logs with async transport mode when CELERY_WORKER_MAX_TASKS_PER_CHILD = 1. Sync HttpTransport fixes it and works fine, but it's
obviously at the cost of being sync. This should be removed and set back to the default if it gets fixed:

# settings/base.py

from raven.transport import HTTPTransport
RAVEN_CONFIG = {
    'transport': HTTPTransport
}