Cleanup most pylint errors in json_schema_compiler.

tools/json_schema_compiler/schema_loader.py

 # 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 sys
 
 import idl_schema
 import json_schema
@@ skipping 36 matching lines @@
                path,
                include_rules,
                cpp_namespace_pattern):
     self._root = root
     self._include_rules = [(path, cpp_namespace_pattern)]
     self._include_rules.extend(include_rules)
 
   def ResolveNamespace(self, full_namespace):
     filenames = GenerateFilenames(full_namespace)
     for path, cpp_namespace in self._include_rules:
+      cpp_namespace_environment = None
+      if cpp_namespace:
+        cpp_namespace_environment = CppNamespaceEnvironment(cpp_namespace)
       for filename in reversed(filenames):
         filepath = os.path.join(path, filename);
         if os.path.exists(os.path.join(self._root, filepath)):
           return Model().AddNamespace(
               self.LoadSchema(filepath)[0],
               filepath,
-              environment=CppNamespaceEnvironment(cpp_namespace))
+              environment=cpp_namespace_environment)
     return None
 
   def ResolveType(self, full_name, default_namespace):
     name_parts = full_name.rsplit('.', 1)
     if len(name_parts) == 1:
       if full_name not in default_namespace.types:
         return None
       return default_namespace
     full_namespace, type_name = full_name.rsplit('.', 1)
     namespace = self.ResolveNamespace(full_namespace)
     if namespace and type_name in namespace.types:
       return namespace
     return None
 
   def LoadSchema(self, schema):
     '''Load a schema definition. The schema parameter must be a file name
     with the full path relative to the root.'''
-    schema_filename, schema_extension = os.path.splitext(schema)
+    schema_extension = os.path.splitext(schema)[1]

[not at google - send to devlin, 2015/01/14 22:44:41]

ditto

 
     schema_path = os.path.join(self._root, schema)
     if schema_extension == '.json':
       api_defs = json_schema.Load(schema_path)
     elif schema_extension == '.idl':
       api_defs = idl_schema.Load(schema_path)
     else:
       sys.exit('Did not recognize file extension %s for schema %s' %
                (schema_extension, schema))
 
     return api_defs