InFile.load_from_files should try to load only '.in' files

Source/build/scripts/in_file.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 46 matching lines @@
         self.name_dictionaries = []
         self.parameters = copy.deepcopy(default_parameters if default_parameters else {})
         self._defaults = defaults
         self._valid_values = copy.deepcopy(valid_values if valid_values else {})
         self._parse(map(str.strip, lines))
 
     @classmethod
     def load_from_files(self, file_paths, defaults, valid_values, default_parameters):
         lines = []
         for path in file_paths:
+            assert path.endswith(".in")
             with open(os.path.abspath(path)) as in_file:
                 lines += in_file.readlines()
         return InFile(lines, defaults, valid_values, default_parameters)
 
     def _is_sequence(self, arg):
         return (not hasattr(arg, "strip")
                 and hasattr(arg, "__getitem__")
                 or hasattr(arg, "__iter__"))
 
     def _parse(self, lines):
@@ skipping 74 matching lines @@
             if self._is_sequence(args[arg_name]):
                 args[arg_name].append(arg_value)
             else:
                 args[arg_name] = arg_value
         return args
 
     def _fatal(self, message):
         # FIXME: This should probably raise instead of exit(1)
         print message
         exit(1)