RedBeatScheduler does not receive lock_timeout from app config

[concreted]

After updating exampleconf.py to include:

REDBEAT_LOCK_TIMEOUT = 15

Running PYTHONPATH=. celery beat --config exampleconf still shows the default lock_timeout:

(.venv) Arics-MacBook-Pro:redbeat aric$ PYTHONPATH=. celery beat --config exampleconf
celery beat v4.0.2 (latentcall) is starting.
__    -    ... __   -        _
LocalTime -> 2017-06-16 12:04:19
Configuration ->
    . broker -> redis://localhost:6379//
    . loader -> celery.loaders.default.Loader
    . scheduler -> redbeat.schedulers.RedBeatScheduler
       . redis -> redis://
       . lock -> `redbeat::lock` 25.00 minutes (1500s)
    . logfile -> [stderr]@%WARNING
    . maxinterval -> 5.00 seconds (5s)

Checking the redbeat::lock key in Redis, it shows a TTL of 1500s rather than 15.