Fix typo in dartdomgenerator.py.

lib/dom/scripts/dartdomgenerator.py

 #!/usr/bin/python
 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. 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 the entry point to create Dart APIs from the IDL database."""
 
 import dartgenerator
 import database
 import logging.config
@@ skipping 133 matching lines @@
                          ['html/dartium', 'html/impl', 'html', ''],
                          {'DARTIUM': True, 'FROG': False}),
           target_database, emitters, auxiliary_dir,
           output_dir)
     elif system == 'native':
       implementation_system = NativeImplementationSystem(
           TemplateLoader(template_dir, ['dom/native', 'dom', '']),
           target_database, html_renames, emitters, auxiliary_dir,
           output_dir)
     else:
-      raise Exception('Unsupported system %s' % system_name)
+      raise Exception('Unsupported system %s' % system)
 
     # Makes interface files available for listing in the library for the
     # implementation system.
     implementation_system._interface_system = interface_system
 
     for system in [interface_system, implementation_system]:
       generator.Generate(target_database, system,
                          source_filter=['WebKit', 'Dart'],
                          super_database=common_database,
                          common_prefix='common',
@@ skipping 54 matching lines @@
 
   dom_output_dir = options.output_dir or os.path.join(current_dir,
       '../generated')
   html_output_dir = options.output_dir or os.path.join(current_dir,
       '../../html/generated')
   Generate(systems, database_dir, options.use_database_cache,
               dom_output_dir, html_output_dir)
 
 if __name__ == '__main__':
   sys.exit(main())