Looking into this, the error is being caused by pool_scrub.py trying to log an APIException, changing lines 39 and 78 to:
logger.exception(e.detail)
allows the script to complete without error, afterwards in my log I see this:
[u'Invalid api end point: http://127.0.0.1:8000/api/pools/Primary/scrub']
[u'Invalid api end point: http://127.0.0.1:8000/api/pools/Primary/scrub/status']
Someone change the REST api recently?