Add transmit lib error test
user
```clojure
(ns cmr.transmit.test.echo.rest
  "Tests for cmr.transmit.echo.rest namespace"
  (:require [clojure.test :refer :all]
            [cmr.transmit.echo.rest :as rest]))

(deftest test-error-masked
  (let [error-message "Unexpected error message: Token 123 does not exist."
       status 500]
    (is (= (format "Unexpected status %d from response. body: %s" status "Token does not exist")
           (rest/unexpected-status-error! status error-message)))))
```
assistant