def _make_mime_boundary(self):
        """Create a mime boundary.

        This exists because mimetools.choose_boundary() is gone in Python 3.x,
        and email.generator._make_boundary isn't really appropriate to use
        here.
        """
        fmt = '%%0%dd' % len(repr(sys.maxsize - 1))
        token = random.randrange(sys.maxsize)
        return (b'=' * 15) + (fmt % token).encode('utf-8') + b'=='
dataset/ETHPy150Open reviewboard/rbtools/rbtools/api/request.py/HttpRequest._make_mime_boundary/original