def set_assume_tty(assume_tty):
    """
    Change whether Rally should assume a tty. If ``True`` is provided, output will be printed. If ``False`` is provided,
    Rally will explicitly check whether it is attached to a tty before attempting to print anything.

    :param assume_tty: Flag indicating whether to assume a tty is attached without checking.
    """
    global ASSUME_TTY
    ASSUME_TTY = assume_tty
