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- Database connections didn't invalidate cache entries when conflict
  errors were raised in response to checkCurrentSerialInTransaction
  errors. Normally, this shouldn't be a problem, since there should be
  pending invalidations for these oids which will cause the object to
  be invalidated. There have been issues with ZEO persistent cache
  management that have caused out of date data to remain in the cache.
  (It's possible that the last of these were addressed in the
  3.10.0b5.) Invalidating read data when there is a conflict error
  provides some extra insurance.