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.

def exit_cleanly(errnum=None):
    """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.
    """
    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))