[NaCl SDK] Convert python scripts from optparse to argparse.

native_client_sdk/src/build_tools/parse_dsc.py

 #!/usr/bin/env python
 # Copyright (c) 2013 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 argparse
 import collections
 import fnmatch
-import optparse
 import os
 import sys
 
 VALID_TOOLCHAINS = [
   'bionic',
   'newlib',
   'glibc',
   'pnacl',
   'win',
   'linux',
@@ skipping 218 matching lines @@
   return True
 
 
 def PrintProjectTree(tree):
   for key in tree:
     print key + ':'
     for val in tree[key]:
       print '\t' + val['NAME']
 
 
-def main(argv):
-  parser = optparse.OptionParser(usage='%prog [options] <dir>')
-  parser.add_option('-e', '--experimental',
+def main(args):
+  parser = argparse.ArgumentParser(description=__doc__)
+  parser.add_argument('-e', '--experimental',
       help='build experimental examples and libraries', action='store_true')
-  parser.add_option('-t', '--toolchain',
+  parser.add_argument('-t', '--toolchain',
       help='Build using toolchain. Can be passed more than once.',
       action='append')
+  parser.add_argument('project_root', default='.')
 
-  options, args = parser.parse_args(argv)
+  options = parser.parse_args(args)
   filters = {}
 
-  load_from_dir = '.'
-  if len(args) > 1:
-    parser.error('Expected 0 or 1 args, got %d.' % len(args))
-
-  if args:
-    load_from_dir = args[0]
-
   if options.toolchain:
     filters['TOOLS'] = options.toolchain
 
   if not options.experimental:
     filters['EXPERIMENTAL'] = False
 
   try:
-    tree = LoadProjectTree(load_from_dir, include=filters)
+    tree = LoadProjectTree(options.project_root, include=filters)
   except ValidationError as e:
     sys.stderr.write(str(e) + '\n')
     return 1
 
   PrintProjectTree(tree)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))