Eventlet is deprecated - should move to a new system

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This message:

kazoo/handlers/eventlet.py:12
  /home/runner/work/kazoo/kazoo/kazoo/handlers/eventlet.py:12: EventletDeprecationWarning: 
  Eventlet is deprecated. It is currently being maintained in bugfix mode, and
  we strongly recommend against using it for new projects.
  
  If you are already using Eventlet, we recommend migrating to a different
  framework.  For more detail see
  https://eventlet.readthedocs.io/en/latest/asyncio/migration.html