User-callable function to return a unique temporary file name. The
file is not created.
Arguments are similar to mkstemp, except that the 'text' argument is
not accepted, and suffix=None, prefix=None and bytes file names are not
supported.
THIS FUNCTION IS UNSAFE AND SHOULD NOT BE USED. The file name may
refer to a file that did not exist at some point, but by the time
you get around to creating it, someone else may have beaten you to
the punch.