Fixes tests broken by issue #27781.

Lib/test/test_genericpath.py

@@ -388,10 +388,13 @@ class CommonTest(GenericTest):
             warnings.simplefilter("ignore", DeprecationWarning)
             self.assertIn(b"foo", self.pathmodule.abspath(b"foo"))
 
+        # avoid UnicodeDecodeError on Windows
+        undecodable_path = b'' if sys.platform == 'win32' else b'f\xf2\xf2'
+
         # Abspath returns bytes when the arg is bytes
         with warnings.catch_warnings():
             warnings.simplefilter("ignore", DeprecationWarning)
-            for path in (b'', b'foo', b'f\xf2\xf2', b'/foo', b'C:\\'):
+            for path in (b'', b'foo', undecodable_path, b'/foo', b'C:\\'):
                 self.assertIsInstance(self.pathmodule.abspath(path), bytes)
 
     def test_realpath(self):

Lib/test/test_httpservers.py

@@ -370,6 +370,8 @@ class SimpleHTTPServerTestCase(BaseTestCase):
         return body
 
     @support.requires_mac_ver(10, 5)
+    @unittest.skipIf(sys.platform == 'win32',
+                     'undecodable name cannot be decoded on win32')
     @unittest.skipUnless(support.TESTFN_UNDECODABLE,
                          'need support.TESTFN_UNDECODABLE')
     def test_undecodable_filename(self):

Lib/test/test_shutil.py

@@ -132,8 +132,6 @@ class TestShutil(unittest.TestCase):
         write_file(os.path.join(victim, 'somefile'), 'foo')
         victim = os.fsencode(victim)
         self.assertIsInstance(victim, bytes)
-        win = (os.name == 'nt')
-        with self.assertWarns(DeprecationWarning) if win else ExitStack():
         shutil.rmtree(victim)
 
     @support.skip_unless_symlink

Lib/test/test_sys.py

@@ -10,6 +10,7 @@ import codecs
 import gc
 import sysconfig
 import platform
+import locale
 
 # count the number of test runs, used to create unique
 # strings to intern in test_intern()
@@ -627,6 +628,8 @@ class SysModuleTest(unittest.TestCase):
 
     @unittest.skipUnless(test.support.FS_NONASCII,
                          'requires OS support of non-ASCII encodings')
+    @unittest.skipUnless(sys.getfilesystemencoding() == locale.getpreferredencoding(False),
+                         'requires FS encoding to match locale')
     def test_ioencoding_nonascii(self):
         env = dict(os.environ)
 
@@ -669,8 +672,6 @@ class SysModuleTest(unittest.TestCase):
         fs_encoding = sys.getfilesystemencoding()
         if sys.platform == 'darwin':
             expected = 'utf-8'
-        elif sys.platform == 'win32':
-            expected = 'mbcs'
         else:
             expected = None
         self.check_fsencoding(fs_encoding, expected)