new_contents: #!/usr/bin/env python
  # Copyright (c) 2012 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.
  
  import os
  import re
  import subprocess
  import sys
  
  """Prints the lowest locally available SDK version greater than or equal to a
  given minimum sdk version to standard output.
  
  Usage:
    python find_sdk.py 10.6  # Ignores SDKs < 10.6
  """
  
  from optparse import OptionParser
  
  
  def parse_version(version_str):
    """'10.6' => [10, 6]"""
    return map(int, re.findall(r'(\d+)', version_str))
  
  
  def main():
    parser = OptionParser()
    parser.add_option("--verify",
                      action="store_true", dest="verify", default=False,
                      help="return the sdk argument and warn if it doesn't exist")
    parser.add_option("--sdk_path",
                      action="store", type="string", dest="sdk_path", default="",
                      help="user-specified SDK path; bypasses verification")
    (options, args) = parser.parse_args()
    min_sdk_version = args[0]
  
    job = subprocess.Popen(['xcode-select', '-print-path'],
                           stdout=subprocess.PIPE,
                           stderr=subprocess.STDOUT)
    out, err = job.communicate()
    if job.returncode != 0:
      print >>sys.stderr, out
      print >>sys.stderr, err
      raise Exception(('Error %d running xcode-select, you might have to run '
        '|sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer| '
        'if you are using Xcode 4.') % job.returncode)
    # The Developer folder moved in Xcode 4.3.
    xcode43_sdk_path = os.path.join(
        out.rstrip(), 'Platforms/MacOSX.platform/Developer/SDKs')
    if os.path.isdir(xcode43_sdk_path):
      sdk_dir = xcode43_sdk_path
    else:
      sdk_dir = os.path.join(out.rstrip(), 'SDKs')
    sdks = [re.findall('^MacOSX(10\.\d+)\.sdk$', s) for s in os.listdir(sdk_dir)]
    sdks = [s[0] for s in sdks if s]  # [['10.5'], ['10.6']] => ['10.5', '10.6']
    sdks = [s for s in sdks  # ['10.5', '10.6'] => ['10.6']
            if parse_version(s) >= parse_version(min_sdk_version)]
    if not sdks:
      raise Exception('No %s+ SDK found' % min_sdk_version)
    best_sdk = sorted(sdks, key=parse_version)[0]
  
    if options.verify and best_sdk != min_sdk_version and not options.sdk_path:
      print >>sys.stderr, ''
      print >>sys.stderr, '                                           vvvvvvv'
      print >>sys.stderr, ''
      print >>sys.stderr, \
          'This build requires the %s SDK, but it was not found on your system.' \
          % min_sdk_version
      print >>sys.stderr, \
          'Either install it, or explicitly set mac_sdk in your GYP_DEFINES.'
      print >>sys.stderr, ''
      print >>sys.stderr, '                                           ^^^^^^^'
      print >>sys.stderr, ''
      return min_sdk_version
  
    return best_sdk
  
  
  if __name__ == '__main__':
    if sys.platform != 'darwin':
      raise Exception("This script only runs on Mac")
    print main()
  
subject: Add script to find existing Mac SDK (taken from chromium).