pin pytest-celery
Major new release of pytest-celery now uses docker for its engine to start workers and is clearly broken in our ci. Pin the old version until there is time to fix this properly.
https://github.com/celery/pytest-celery/releases/tag/v1.0.0
Hopefully fix testing on master (1.10, and 1.11 work because they have fixed environments)
Edited by Stuart Fisher