Extension docs server: fix errors in preview.py.

chrome/common/extensions/docs/server2/preview.py

 #!/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.
 
 # This is a preview server for the apps and extensions docs. Navigate to a docs
 # page, and the page will be rendered how it will be on the production server.
 #
 # For example: http://localhost:8000/tabs.html will render the docs page for
 # the tabs API.
@@ skipping 37 matching lines @@
     content = response.out.getvalue()
     if isinstance(content, str):
       self.wfile.write(content)
     else:
       self.wfile.write(content.encode('utf-8', 'replace'))
 
 if __name__ == '__main__':
   parser = optparse.OptionParser(
       description='Runs a server to preview the extension documentation.',
       usage='usage: %prog [option]...')
-  parser.add_option('-p', '--port', default=8000,
+  parser.add_option('-p', '--port', default="8000",
       help='port to run the server on')
 
   (opts, argv) = parser.parse_args()
 
+  print('Starting previewserver on port %s' % opts.port)
+  print('The extension documentation can be found at:')
+  print('')
+  print('  http://localhost:%s' % opts.port)
+  print('')
+
+  server = HTTPServer(('', int(opts.port)), RequestHandler)
   try:
-    print('Starting previewserver on port %d' % opts.port)
-    print('The extension documentation can be found at:')
-    print('')
-    print('  http://localhost:%d' % opts.port)
-    print('')
-
-    server = HTTPServer(('', int(opts.port)), RequestHandler)
     server.serve_forever()
   except KeyboardInterrupt:
     pass
   finally:
     server.socket.close()