code: def exit_cleanly(errnum=None):
      
      default = "An Unknown Error has Occurred!"
      cases = {errno.EINVAL: "Improper or invalid input value",
               errno.ESPIPE: "Could not complete action due to a broken" +
               " dependency",
               errno.ENOSYS: "Could not complete action due to unexpected setup",
               errno.EIO: "Could not access an expected file",
               errno.EPERM: "Could not access an item due to permissions issues",
               -1: default}
      help_stmt = """
  %s [--opt [option]]
      With opts:
          working_directory - ONLY use this if you're overwriting `pwd`!
      """ % (sys.argv[0])
      if not errnum:
          errnum = 0
      elif not isinstance(errnum, int) and hasattr(errno, errnum):
          errnum = getattr(errno, errnum)
      try:
          errnum = int(errnum)
      except TypeError:
          errnum = -1
      if errnum == 0:
          help_stmt = ''
          stmt = "Successful in configuration!"
      elif errnum in cases:
          stmt = cases[errnum]
      else:
          stmt = default
      print("%s\n\n%s" % (stmt, help_stmt))
docs: exit_cleanly
  
  Exits the runtime cleanly using SystemExit.  This is the official, handling
  exception here as this is mostly meant to be a standalone script.