tests fail under python3.9: urllib.parse.unquote accepts bytes

[keszybz]

________________________ UnquotingTests.test_unquoting _________________________

self = <test_future.test_urllib_toplevel.UnquotingTests testMethod=test_unquoting>

    def test_unquoting(self):
        # Make sure unquoting of all ASCII values works
        escape_list = []
        for num in range(128):
            given = hexescape(chr(num))
            expect = chr(num)
            result = urllib_parse.unquote(given)
            self.assertEqual(expect, result,
                             "using unquote(): %r != %r" % (expect, result))
            result = urllib_parse.unquote_plus(given)
            self.assertEqual(expect, result,
                             "using unquote_plus(): %r != %r" %
                             (expect, result))
            escape_list.append(given)
        escape_string = ''.join(escape_list)
        del escape_list
        result = urllib_parse.unquote(escape_string)
        self.assertEqual(result.count('%'), 1,
                         "using unquote(): not all characters escaped: "
                         "%s" % result)
        self.assertRaises((TypeError, AttributeError), urllib_parse.unquote, None)
        self.assertRaises((TypeError, AttributeError), urllib_parse.unquote, ())
        with support.check_warnings(('', BytesWarning), quiet=True):
>           self.assertRaises((TypeError, AttributeError), urllib_parse.unquote, bytes(b''))
E           AssertionError: (<class 'TypeError'>, <class 'AttributeError'>) not raised by unquote

tests/test_future/test_urllib_toplevel.py:785: AssertionError

python3.8:

>>> import urllib.parse
>>> urllib.parse.unquote(b'')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib64/python3.7/urllib/parse.py", line 609, in unquote
    if '%' not in string:
TypeError: a bytes-like object is required, not 'str'

python3.9:

>>> import urllib.parse
>>> urllib.parse.unquote(b'')
''