some problems with quickstart example

[holtzermann17]

Here's what I'm seeing when I run the quickstart example

(with-open [in  (clojure.java.io/input-stream  "README.md")             
            out (clojure.java.io/output-stream "line_count.txt")]
  (->pipe->                                           
   in
   [(exec ["grep" "java"])
    (exec ["wc" "-l"])]
   out))
;=> #pipes.job/job-ctl/reify--21836[{:status :pending, :val nil} 0x32e24e7f]
;;  Exception in thread "Exec Default Executor" java.io.IOException: Stream Closed
;;  at java.io.FileOutputStream.writeBytes(Native Method)
;;  at java.io.FileOutputStream.write(FileOutputStream.java:326)
;;  at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
;;  at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
;;  at java.io.FilterOutputStream.close(FilterOutputStream.java:158)
;;  at clj_commons_exec.DefaultResultHandler.onProcessFailed(clj_commons_exec.clj:50)
;;  at org.apache.commons.exec.DefaultExecutor$1.run(DefaultExecutor.java:205)
;;  at java.lang.Thread.run(Thread.java:745)
(slurp "line_count.txt")
;=> ""

However, I'm able to run a variant of it with successful output and no error messages.

(def baos (java.io.ByteArrayOutputStream.))
;=> #'flowrweb.core/baos
(with-open [in  (clojure.java.io/input-stream  "README.md") out baos]
  (->pipe->                                           
   in
   [(exec ["cat" "README.md"])                        
    (exec ["wc" "-l"])]
   out))
;=> #pipes.job/job-ctl/reify--11259[{:status :pending, :val nil} 0x11bdd579]
(String. (.toByteArray baos) (. java.nio.charset.Charset defaultCharset))
;=> "157\n"
(.reset baos)
;=> nil