gh-96189: Fix test_invalid_utf8 on a number of build bots (GH-96190)

The clearing of the temporary directory is not working on some platforms and
leaving behind files.

This has been updated to use the pattern in test_cmd_line.py [1] using the
special TESTFN rather than a test directory.

[1] https://github.com/python/cpython/blob/main/Lib/test/test_cmd_line.py#L559

Lib/test/test_source_encoding.py

@@ -239,50 +239,50 @@ def test_invalid_utf8(self):
         # it's an otherwise valid Python source file.
         template = b'"%s"\n'
 
-        with tempfile.TemporaryDirectory() as tmpd:
+        fn = TESTFN
-            fn = os.path.join(tmpd, 'test.py')
+        self.addCleanup(unlink, fn)
 
-            def check(content):
+        def check(content):
-                with open(fn, 'wb') as fp:
+            with open(fn, 'wb') as fp:
-                    fp.write(template % content)
+                fp.write(template % content)
-                script_helper.assert_python_failure(fn)
+            script_helper.assert_python_failure(fn)
 
-            # continuation bytes in a sequence of 2, 3, or 4 bytes
+        # continuation bytes in a sequence of 2, 3, or 4 bytes
-            continuation_bytes = [bytes([x]) for x in range(0x80, 0xC0)]
+        continuation_bytes = [bytes([x]) for x in range(0x80, 0xC0)]
-            # start bytes of a 2-byte sequence equivalent to code points < 0x7F
+        # start bytes of a 2-byte sequence equivalent to code points < 0x7F
-            invalid_2B_seq_start_bytes = [bytes([x]) for x in range(0xC0, 0xC2)]
+        invalid_2B_seq_start_bytes = [bytes([x]) for x in range(0xC0, 0xC2)]
-            # start bytes of a 4-byte sequence equivalent to code points > 0x10FFFF
+        # start bytes of a 4-byte sequence equivalent to code points > 0x10FFFF
-            invalid_4B_seq_start_bytes = [bytes([x]) for x in range(0xF5, 0xF8)]
+        invalid_4B_seq_start_bytes = [bytes([x]) for x in range(0xF5, 0xF8)]
-            invalid_start_bytes = (
+        invalid_start_bytes = (
-                continuation_bytes + invalid_2B_seq_start_bytes +
+            continuation_bytes + invalid_2B_seq_start_bytes +
-                invalid_4B_seq_start_bytes + [bytes([x]) for x in range(0xF7, 0x100)]
+            invalid_4B_seq_start_bytes + [bytes([x]) for x in range(0xF7, 0x100)]
-            )
+        )
 
-            for byte in invalid_start_bytes:
+        for byte in invalid_start_bytes:
-                check(byte)
+            check(byte)
 
-            for sb in invalid_2B_seq_start_bytes:
+        for sb in invalid_2B_seq_start_bytes:
-                for cb in continuation_bytes:
+            for cb in continuation_bytes:
-                    check(sb + cb)
+                check(sb + cb)
 
-            for sb in invalid_4B_seq_start_bytes:
+        for sb in invalid_4B_seq_start_bytes:
-                for cb1 in continuation_bytes[:3]:
+            for cb1 in continuation_bytes[:3]:
-                    for cb3 in continuation_bytes[:3]:
+                for cb3 in continuation_bytes[:3]:
-                        check(sb+cb1+b'\x80'+cb3)
+                    check(sb+cb1+b'\x80'+cb3)
 
-            for cb in [bytes([x]) for x in range(0x80, 0xA0)]:
+        for cb in [bytes([x]) for x in range(0x80, 0xA0)]:
-                check(b'\xE0'+cb+b'\x80')
+            check(b'\xE0'+cb+b'\x80')
-                check(b'\xE0'+cb+b'\xBF')
+            check(b'\xE0'+cb+b'\xBF')
-                # surrogates
+            # surrogates
-            for cb in [bytes([x]) for x in range(0xA0, 0xC0)]:
+        for cb in [bytes([x]) for x in range(0xA0, 0xC0)]:
-                check(b'\xED'+cb+b'\x80')
+            check(b'\xED'+cb+b'\x80')
-                check(b'\xED'+cb+b'\xBF')
+            check(b'\xED'+cb+b'\xBF')
-            for cb in [bytes([x]) for x in range(0x80, 0x90)]:
+        for cb in [bytes([x]) for x in range(0x80, 0x90)]:
-                check(b'\xF0'+cb+b'\x80\x80')
+            check(b'\xF0'+cb+b'\x80\x80')
-                check(b'\xF0'+cb+b'\xBF\xBF')
+            check(b'\xF0'+cb+b'\xBF\xBF')
-            for cb in [bytes([x]) for x in range(0x90, 0xC0)]:
+        for cb in [bytes([x]) for x in range(0x90, 0xC0)]:
-                check(b'\xF4'+cb+b'\x80\x80')
+            check(b'\xF4'+cb+b'\x80\x80')
-                check(b'\xF4'+cb+b'\xBF\xBF')
+            check(b'\xF4'+cb+b'\xBF\xBF')
 
 
 class BytesSourceEncodingTest(AbstractSourceEncodingTest, unittest.TestCase):