old_contents: """Utility functionality."""
  
  import os
  
  from aiohttp import web_exceptions
  
  API_TOKEN_ENV = 'SLACK_API_TOKEN'
  """The environment variable to store the user's API token in."""
  
  
  class FriendlyError(Exception):
      """Exception with friendlier error messages.
  
        Notes:
          The ``err_msg`` is resolved in :py:attr:`EXPECTED_ERRORS`,
          or passed through as-is if not found there.
  
        Arguments:
          err_msg (:py:class:`str`): The error message to attempt to
            resolve.
          *args (:py:class:`tuple`): Any additional positional arguments.
  
      """
  
      EXPECTED_ERRORS = {}
      """Friendly messages for expected errors."""
  
      def __init__(self, err_msg, *args):
          super().__init__(self.EXPECTED_ERRORS.get(err_msg, err_msg), *args)
  
  
  def raise_for_status(response):
      """Raise an appropriate error for a given response.
  
      Arguments:
        response (:py:class:`aiohttp.ClientResponse`): The API response.
  
      Raises:
        :py:class:`aiohttp.web_exceptions.HTTPException`: The appropriate
          error for the response's status.
  
      """
      for err_name in web_exceptions.__all__:
          err = getattr(web_exceptions, err_name)
          if err.status_code == response.status:
              payload = dict(
                  headers=response.headers,
                  reason=response.reason,
              )
              if issubclass(err, web_exceptions._HTTPMove):
                  raise err(response.headers['Location'], **payload)
              raise err(**payload)
  
  
  def get_api_token():
      """Allow the user to enter their API token.
  
      Note:
        The token is added to the environment using the variable defined
        in :py:attr:`API_TOKEN_ENV`.
  
      Returns:
        :py:class:`str`: The user's API token.
  
      """
      token = os.getenv(API_TOKEN_ENV)
      if token:
          return token
      template = ('Enter your API token (this will be stored '
                  'as {} for future use): ').format(API_TOKEN_ENV)
      token = input(template)
      os.environ[API_TOKEN_ENV] = token
      return token
  
new_contents: """Utility functionality."""
  
  import os
  
  from aiohttp import web_exceptions
  
  API_TOKEN_ENV = 'SLACK_API_TOKEN'
  """The environment variable to store the user's API token in."""
  
  
  class FriendlyError(Exception):
      """Exception with friendlier error messages.
  
        Notes:
          The ``err_msg`` is resolved in :py:data:`EXPECTED_ERRORS`,
          or passed through as-is if not found there.
  
        Arguments:
          err_msg (:py:class:`str`): The error message to attempt to
            resolve.
          *args (:py:class:`tuple`): Any additional positional arguments.
  
      """
  
      EXPECTED_ERRORS = {}
      """Friendly messages for expected errors."""
  
      def __init__(self, err_msg, *args):
          super().__init__(self.EXPECTED_ERRORS.get(err_msg, err_msg), *args)
  
  
  def raise_for_status(response):
      """Raise an appropriate error for a given response.
  
      Arguments:
        response (:py:class:`aiohttp.ClientResponse`): The API response.
  
      Raises:
        :py:class:`aiohttp.web_exceptions.HTTPException`: The appropriate
          error for the response's status.
  
      """
      for err_name in web_exceptions.__all__:
          err = getattr(web_exceptions, err_name)
          if err.status_code == response.status:
              payload = dict(
                  headers=response.headers,
                  reason=response.reason,
              )
              if issubclass(err, web_exceptions._HTTPMove):
                  raise err(response.headers['Location'], **payload)
              raise err(**payload)
  
  
  def get_api_token():
      """Allow the user to enter their API token.
  
      Note:
        The token is added to the environment using the variable defined
        in :py:attr:`API_TOKEN_ENV`.
  
      Returns:
        :py:class:`str`: The user's API token.
  
      """
      token = os.getenv(API_TOKEN_ENV)
      if token:
          return token
      template = ('Enter your API token (this will be stored '
                  'as {} for future use): ').format(API_TOKEN_ENV)
      token = input(template)
      os.environ[API_TOKEN_ENV] = token
      return token
  
subject: Correct documentation cross-reference