[subprocess2] Replace VOID with DEVNULL

subprocess.DEVNULL was introduced in Python3 to serve same purpose
as subprocess2.VOID, so rename VOID to DEVNULL in subprocess2.

Change-Id: I6dade3306ffc3bc2441ac6083f362b099c2427e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2587758
Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

subprocess2.py

@@ -21,18 +21,18 @@ import threading
 if sys.version_info.major == 2:
   import Queue
   codecs.lookup('string-escape')
+  # Sends stdout or stderr to os.devnull.
+  DEVNULL = open(os.devnull, 'r+')
 else:
   import queue as Queue
   # pylint: disable=redefined-builtin
   basestring = (str, bytes)
+  DEVNULL = subprocess.DEVNULL
 
 
 # Constants forwarded from subprocess.
 PIPE = subprocess.PIPE
 STDOUT = subprocess.STDOUT
-# Sends stdout or stderr to os.devnull.
-VOID = open(os.devnull, 'w')
-VOID_INPUT = open(os.devnull, 'r')
 
 
 class CalledProcessError(subprocess.CalledProcessError):
@@ -107,7 +107,7 @@ class Popen(subprocess.Popen):
     in English.
   - Sets shell=True on windows by default. You can override this by forcing
     shell parameter to a value.
-  - Adds support for VOID to not buffer when not needed.
+  - Adds support for DEVNULL to not buffer when not needed.
   - Adds self.start property.
 
   Note: Popen() can throw OSError when cwd or args[0] doesn't exist. Translate
@@ -197,16 +197,16 @@ def communicate(args, **kwargs):
 def call(args, **kwargs):
   """Emulates subprocess.call().
 
-  Automatically convert stdout=PIPE or stderr=PIPE to VOID.
+  Automatically convert stdout=PIPE or stderr=PIPE to DEVNULL.
   In no case they can be returned since no code path raises
   subprocess2.CalledProcessError.
 
   Returns exit code.
   """
   if kwargs.get('stdout') == PIPE:
-    kwargs['stdout'] = VOID
+    kwargs['stdout'] = DEVNULL
   if kwargs.get('stderr') == PIPE:
-    kwargs['stderr'] = VOID
+    kwargs['stderr'] = DEVNULL
   return communicate(args, **kwargs)[1]
 
 
@@ -236,7 +236,7 @@ def capture(args, **kwargs):
   - Discards returncode.
   - Blocks stdin by default if not specified since no output will be visible.
   """
-  kwargs.setdefault('stdin', VOID_INPUT)
+  kwargs.setdefault('stdin', DEVNULL)
 
   # Like check_output, deny the caller from using stdout arg.
   return communicate(args, stdout=PIPE, **kwargs)[0][0]
@@ -252,7 +252,7 @@ def check_output(args, **kwargs):
   - Blocks stdin by default if not specified since no output will be visible.
   - As per doc, "The stdout argument is not allowed as it is used internally."
   """
-  kwargs.setdefault('stdin', VOID_INPUT)
+  kwargs.setdefault('stdin', DEVNULL)
   if 'stdout' in kwargs:
     raise ValueError('stdout argument not allowed, it would be overridden.')
   return check_call_out(args, stdout=PIPE, **kwargs)[0]