Apply suggestions from code review

Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>

Author: mdboom

Lib/test/test_source_encoding.py

@@ -14,11 +14,11 @@ class MiscSourceEncodingTest(unittest.TestCase):
 
     def test_pep263(self):
         self.assertEqual(
-            "ðÉÔÏÎ".encode("utf-8"),
+            "ðÉÔÏÎ".encode("utf-8"),
             b'\xd0\x9f\xd0\xb8\xd1\x82\xd0\xbe\xd0\xbd'
         )
         self.assertEqual(
-            "\ð".encode("utf-8"),
+            "\ð".encode("utf-8"),
             b'\\\xd0\x9f'
         )
 
@@ -251,8 +251,8 @@ def check(content):
             # We want to assert that the python subprocess failed gracefully,
             # not via a signal.
             self.assertGreaterEqual(rc, 1)
-            self.assertTrue(b"Non-UTF-8 code starting with" in stderr)
-            self.assertTrue(b"on line 5" in stderr)
+            self.assertIn(b"Non-UTF-8 code starting with", stderr)
+            self.assertIn(b"on line 5", stderr)
 
         # continuation bytes in a sequence of 2, 3, or 4 bytes
         continuation_bytes = [bytes([x]) for x in range(0x80, 0xC0)]