Use assertIsNone. Thanks Terry Reedy.

Lib/importlib/test/builtin/test_finder.py

@@ -35,14 +35,14 @@ class FinderTests(abc.FinderTests):
     def test_failure(self):
         assert 'importlib' not in sys.builtin_module_names
         loader = machinery.BuiltinImporter.find_module('importlib')
-        self.assertIs(loader, None)
+        self.assertIsNone(loader)
 
     def test_ignore_path(self):
         # The value for 'path' should always trigger a failed import.
         with util.uncache(builtin_util.NAME):
             loader = machinery.BuiltinImporter.find_module(builtin_util.NAME,
                                                             ['pkg'])
-            self.assertIs(loader, None)
+            self.assertIsNone(loader)
 
 
 

Lib/importlib/test/builtin/test_loader.py

@@ -74,12 +74,12 @@ class InspectLoaderTests(unittest.TestCase):
     def test_get_code(self):
         # There is no code object.
         result = machinery.BuiltinImporter.get_code(builtin_util.NAME)
-        self.assertIs(result, None)
+        self.assertIsNone(result)
 
     def test_get_source(self):
         # There is no source.
         result = machinery.BuiltinImporter.get_source(builtin_util.NAME)
-        self.assertIs(result, None)
+        self.assertIsNone(result)
 
     def test_is_package(self):
         # Cannot be a package.

Lib/importlib/test/extension/test_finder.py

@@ -36,7 +36,7 @@ class FinderTests(abc.FinderTests):
         pass
 
     def test_failure(self):
-        self.assertIs(self.find_module('asdfjkl;'), None)
+        self.assertIsNone(self.find_module('asdfjkl;'))
 
     # XXX Raise an exception if someone tries to use the 'path' argument?
 

Lib/importlib/test/frozen/test_finder.py

@@ -35,7 +35,7 @@ class FinderTests(abc.FinderTests):
 
     def test_failure(self):
         loader = self.find('<not real>')
-        self.assertIs(loader, None)
+        self.assertIsNone(loader)
 
 
 def test_main():

Lib/importlib/test/frozen/test_loader.py

@@ -93,7 +93,7 @@ class InspectLoaderTests(unittest.TestCase):
     def test_get_source(self):
         # Should always return None.
         result = machinery.FrozenImporter.get_source('__hello__')
-        self.assertIs(result, None)
+        self.assertIsNone(result)
 
     def test_is_package(self):
         # Should be able to tell what is a package.

Lib/importlib/test/import_/test_meta_path.py

@@ -82,7 +82,7 @@ class CallSignature(unittest.TestCase):
                 self.assertEqual(len(args), 2)
                 self.assertEqual(len(kwargs), 0)
                 self.assertEqual(args[0], mod_name)
-                self.assertIs(args[1], None)
+                self.assertIsNone(args[1])
 
     def test_with_path(self):
         # [path set]

Lib/importlib/test/import_/test_path.py

@@ -20,7 +20,7 @@ class FinderTests(unittest.TestCase):
         # Test None returned upon not finding a suitable finder.
         module = '<test module>'
         with util.import_state():
-            self.assertIs(machinery.PathFinder.find_module(module), None)
+            self.assertIsNone(machinery.PathFinder.find_module(module))
 
     def test_sys_path(self):
         # Test that sys.path is used when 'path' is None.

Lib/importlib/test/source/test_finder.py

@@ -115,7 +115,7 @@ class FinderTests(abc.FinderTests):
     def test_failure(self):
         with source_util.create_modules('blah') as mapping:
             nothing = self.import_(mapping['.root'], 'sdfsadsadf')
-            self.assertIs(nothing, None)
+            self.assertIsNone(nothing)
 
     def test_empty_string_for_dir(self):
         # The empty string from sys.path means to search in the cwd.

Lib/importlib/test/test_locks.py

@@ -97,7 +97,7 @@ class LifetimeTests(unittest.TestCase):
         del lock
         support.gc_collect()
         self.assertNotIn(name, _bootstrap._module_locks)
-        self.assertIs(wr(), None)
+        self.assertIsNone(wr())
 
     def test_all_locks(self):
         support.gc_collect()