CAS mismatch exception is a raw rpc error

15:47:59.262 [-thread-22] INFO  client.util.ExceptionValidator - Unexpected result on exception {

  other {

    serialized: "rpc error: code = FailedPrecondition desc = rpc error: code = FailedPrecondition desc = The specified CAS for \'a8372da4-88e8-4af6-bed0-0d4db20890ae\' in \'default/_default/_default\' did not match. | {\"context\":{\"details\":1,\"precondition_violation\":\"CAS\",\"server\":\"The specified CAS for \'a8372da4-88e8-4af6-bed0-0d4db20890ae\' in \'default/_default/_default\' did not match.\"}} | {\"context\":{\"details\":1,\"precondition_violation\":\"CAS\",\"server\":\"rpc error: code = FailedPrecondition desc = The specified CAS for \'a8372da4-88e8-4af6-bed0-0d4db20890ae\' in \'default/_default/_default\' did not match. | {\\\"context\\\":{\\\"details\\\":1,\\\"precondition_violation\\\":\\\"CAS\\\",\\\"server\\\":\\\"The specified CAS for \'a8372da4-88e8-4af6-bed0-0d4db20890ae\' in \'default/_default/_default\' did not match.\\\"}}\"}}"

  }

}