Test fixes for Python 3.9

Fixes PythonCharmers#540
Fixes PythonCharmers#541

Author: hroncok

src/future/moves/_dummy_thread.py

@@ -2,7 +2,7 @@
 from future.utils import PY3
 
 if PY3:
-    from _dummy_thread import *
+    from _thread import *
 else:
     __future_module__ = True
     from dummy_thread import *

src/future/standard_library/__init__.py

@@ -125,7 +125,7 @@
            # 'Tkinter': 'tkinter',
            '_winreg': 'winreg',
            'thread': '_thread',
-           'dummy_thread': '_dummy_thread',
+           'dummy_thread': '_thread',
            # 'anydbm': 'dbm',   # causes infinite import loop
            # 'whichdb': 'dbm',  # causes infinite import loop
            # anydbm and whichdb are handled by fix_imports2

tests/test_future/test_standard_library.py

@@ -422,7 +422,6 @@ def test_urllib_imports_install_hooks(self):
 
     def test_underscore_prefixed_modules(self):
         import _thread
-        import _dummy_thread
         import _markupbase
         self.assertTrue(True)
 

tests/test_future/test_urllib_toplevel.py

@@ -781,8 +781,6 @@ def test_unquoting(self):
                          "%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''))
 
     def test_unquoting_badpercent(self):
         # Test unquoting on bad percent-escapes