old_contents: from __future__ import print_function
  
  import sys
  
  
  def error(message, exit=True):
      """Print an error message and optionally exit."""
  
      assert isinstance(message, str), "message must be a str"
      assert isinstance(exit, bool), "exit must be a bool"
  
      print("error:", message, file=sys.stderr)
      if exit:
          sys.exit(1)
  
  
  def info(message, quiet=False):
      """Print a simple info message."""
  
      if not quiet:
          print(message)
  
new_contents: from __future__ import print_function
  
  import sys
  
  
  def error(message, exit=True):
      """Print an error message and optionally exit."""
  
      assert isinstance(message, str), "message must be a str"
      assert isinstance(exit, bool), "exit must be a bool"
  
      print("error:", message, file=sys.stderr)
      if exit:
          sys.exit(1)
  
  
  def warn(message):
      """Print a simple warning message."""
      info('warn: {}'.format(message), False)
  
  
  def usage(message):
      """Print a simple usage message."""
      info('usage: {}'.format(message), False)
  
  
  def info(message, quiet=False):
      """Print a simple info message."""
  
      if not quiet:
          print(message)
  
subject: Add warn and usage message options