Adapted the pipe() code to python3; API changes and str/byte handling.

- Legacy-Id: 16345

ietf/utils/pipe.py

@@ -1,27 +1,28 @@
+# Copyright The IETF Trust 2010-2019, All Rights Reserved
 # Simplified interface to os.popen3()
 
-def pipe(cmd, str=None):
-    from popen2 import Popen3 as Popen
+def pipe(cmd:bytes, str:bytes=None) -> (int, bytes, bytes):
+    from subprocess import Popen, PIPE
     bufsize = 4096
     MAX = 65536*16
 
     if str and len(str) > 4096:                 # XXX: Hardcoded Linux 2.4, 2.6 pipe buffer size
         bufsize = len(str)
 
-    pipe = Popen(cmd, True, bufsize)
+    pipe = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE, bufsize=bufsize, shell=True)
     if not str is None:
-        pipe.tochild.write(str)
-        pipe.tochild.close()
+        pipe.stdin.write(str)
+        pipe.stdin.close()
 
-    out = ""
-    err = ""
+    out = b""
+    err = b""
     while True:
-        str = pipe.fromchild.read()
+        str = pipe.stdout.read()
         if str:
             out += str
         code = pipe.poll()
         if code > -1:
-            err = pipe.childerr.read()
+            err = pipe.stderr.read()
             break
         if len(out) >= MAX:
             err = "Output exceeds %s bytes and has been truncated" % MAX