old_contents: # encoding: utf-8
  
  """
  .. codeauthor:: Tsuyoshi Hombashi <tsuyoshi.hombashi@gmail.com>
  """
  
  from __future__ import absolute_import, unicode_literals
  
  
  class CommandError(Exception):
      @property
      def errno(self):
          return self.__errno
  
      def __init__(self, *args, **kwargs):
          self.__errno = kwargs.pop("errno", None)
  
          super(CommandError, self).__init__(*args, **kwargs)
  
  
  class InvalidCommandError(CommandError):
      # Deprecate in the future
      pass
  
  
  class CommandNotFoundError(CommandError):
      # Deprecate in the future
      pass
  
new_contents: # encoding: utf-8
  
  """
  .. codeauthor:: Tsuyoshi Hombashi <tsuyoshi.hombashi@gmail.com>
  """
  
  from __future__ import absolute_import, unicode_literals
  
  
  class CommandError(Exception):
      @property
      def cmd(self):
          return self.__cmd
  
      @property
      def errno(self):
          return self.__errno
  
      def __init__(self, *args, **kwargs):
          self.__cmd = kwargs.pop("cmd", None)
          self.__errno = kwargs.pop("errno", None)
  
          super(CommandError, self).__init__(*args, **kwargs)
  
  
  class InvalidCommandError(CommandError):
      # Deprecate in the future
      pass
  
  
  class CommandNotFoundError(CommandError):
      # Deprecate in the future
      pass
  
subject: Add a property to an exception class