The :mod:`tkinter.filedialog` functions that return a filename
(:func:`~tkinter.filedialog.askopenfilename`,
:func:`~tkinter.filedialog.asksaveasfilename` and
:func:`~tkinter.filedialog.askdirectory`) now consistently return an empty
string when the dialog is cancelled, instead of an empty tuple or ``b''``
on some platforms.  :func:`~tkinter.filedialog.askopenfilenames` likewise
always returns an empty tuple, and :func:`~tkinter.filedialog.askopenfiles`
an empty list.
