Reapply r79779: "Removed gclient_utils.Popen() and use subprocess2's version instead."

subprocess2.py

 # coding=utf8
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """Collection of subprocess wrapper functions.
 
 In theory you shouldn't need anything else in subprocess, or this module failed.
 """
 
 from __future__ import with_statement
+import errno
 import logging
 import os
 import subprocess
 import sys
 import tempfile
 import time
 import threading
 
 # Constants forwarded from subprocess.
 PIPE = subprocess.PIPE
@@ skipping 96 matching lines @@
   env = env.copy()
   def fix_lang(name):
     if not is_english(name):
       env[name] = 'en_US.UTF-8'
   fix_lang('LANG')
   fix_lang('LANGUAGE')
   return env
 
 
 def Popen(args, **kwargs):
-  """Wraps subprocess.Popen().
+  """Wraps subprocess.Popen() with various workarounds.
 
   Returns a subprocess.Popen object.
 
   - Forces English output since it's easier to parse the stdout if it is always
     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.
 
-  Note: Popen() can throw OSError when cwd or args[0] doesn't exist.
+  Note: Popen() can throw OSError when cwd or args[0] doesn't exist. Translate
+  exceptions generated by cygwin when it fails trying to emulate fork().
   """
   # Make sure we hack subprocess if necessary.
   hack_subprocess()
   add_kill()
 
   env = get_english_env(kwargs.get('env'))
   if env:
     kwargs['env'] = env
 
   if not kwargs.get('shell') is None:
     # *Sigh*:  Windows needs shell=True, or else it won't search %PATH% for the
     # executable, but shell=True makes subprocess on Linux fail when it's called
     # with a list because it only tries to execute the first item in the list.
     kwargs['shell'] = (sys.platform=='win32')
 
   tmp_str = ' '.join(args)
   if kwargs.get('cwd', None):
     tmp_str += ';  cwd=%s' % kwargs['cwd']
   logging.debug(tmp_str)
 
   # Replaces VOID with handle to /dev/null.
   if kwargs.get('stdout') in (VOID, os.devnull):
     kwargs['stdout'] = open(os.devnull, 'w')
   if kwargs.get('stderr') in (VOID, os.devnull):
     kwargs['stderr'] = open(os.devnull, 'w')
-  return subprocess.Popen(args, **kwargs)
+  try:
+    return subprocess.Popen(args, **kwargs)
+  except OSError, e:
+    if e.errno == errno.EAGAIN and sys.platform == 'cygwin':
+      # Convert fork() emulation failure into a CalledProcessError().
+      raise CalledProcessError(
+          e.errno,
+          args,
+          kwargs.get('cwd'),
+          'Visit '
+          'http://code.google.com/p/chromium/wiki/CygwinDllRemappingFailure to '
+          'learn how to fix this error; you need to rebase your cygwin dlls',
+          None)
+    raise
 
 
 def call(args, timeout=None, **kwargs):
   """Wraps subprocess.Popen().communicate().
 
   Returns ((stdout, stderr), returncode).
 
   - The process will be kill with error code -9 after |timeout| seconds if set.
   - Automatically passes stdin content as input so do not specify stdin=PIPE.
   """
@@ skipping 69 matching lines @@
 
   Returns stdout.
 
   - Discards stderr. By default sets stderr=STDOUT.
   - Throws if return code is not 0.
   - Works even prior to python 2.7.
   """
   if kwargs.get('stderr') is None:
     kwargs['stderr'] = STDOUT
   return check_call(args, stdout=PIPE, **kwargs)[0]