Cleanup most pylint errors in json_schema_compiler.

tools/json_schema_compiler/compiler.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.
 """Generator for C++ structs from api json files.
 
 The purpose of this tool is to remove the need for hand-written code that
 converts to and from base::Value types when receiving javascript api calls.
 Originally written for generating code for extension apis. Reference schemas
 are in chrome/common/extensions/api.
@@ skipping 67 matching lines @@
                                            cpp_namespace_pattern))
 
     if default_namespace is None:
       default_namespace = namespace
 
     if src_path is None:
       src_path = namespace.source_file_dir
     else:
       src_path = os.path.commonprefix((src_path, namespace.source_file_dir))
 
-    path, filename = os.path.split(file_path)
+    _, filename = os.path.split(file_path)
     filename_base, _ = os.path.splitext(filename)
 
   # Construct the type generator with all the namespaces in this model.
   type_generator = CppTypeGenerator(api_model,
                                     schema_loader,
                                     default_namespace)
   if generator_name in ('cpp-bundle-registration', 'cpp-bundle-schema'):
     cpp_bundle_generator = CppBundleGenerator(root,
                                               api_model,
                                               api_defs,
@@ skipping 17 matching lines @@
     generators = [
       ('%s.h' % filename_base, cpp_generator.h_generator),
       ('%s.cc' % filename_base, cpp_generator.cc_generator)
     ]
   elif generator_name == 'dart':
     generators = [
       ('%s.dart' % namespace.unix_name, DartGenerator(
           dart_overrides_dir))
     ]
   else:
-    raise Exception('Unrecognised generator %s' % generator)
+    raise Exception('Unrecognised generator %s' % generator_name)
 
   output_code = []
   for filename, generator in generators:
     code = generator.Generate(namespace).Render()
     if destdir:
       if generator_name == 'cpp-bundle-registration':
         # Function registrations must be output to impl_dir, since they link in
         # API implementations.
         output_dir = os.path.join(destdir, impl_dir)
       else:
@@ skipping 52 matching lines @@
   include_rules = []
   if opts.include_rules:
     include_rules = map(split_path_and_namespace,
                         shlex.split(opts.include_rules))
 
   result = GenerateSchema(opts.generator, file_paths, opts.root, opts.destdir,
                           opts.namespace, opts.dart_overrides_dir,
                           opts.impl_dir, include_rules)
   if not opts.destdir:
     print result