support: temp_dir() and change_cwd() uses repr() in error message

Serhiy Storshaka pointed me that str(path) can emit a BytesWarning: use
repr(path) instead.

Lib/test/support/__init__.py

@@ -958,7 +958,7 @@ def temp_dir(path=None, quiet=False):
             if not quiet:
                 raise
             warnings.warn(f'tests may fail, unable to create '
-                          f'temporary directory {path}: {exc}',
+                          f'temporary directory {path!r}: {exc}',
                           RuntimeWarning, stacklevel=3)
     try:
         yield path
@@ -986,7 +986,7 @@ def change_cwd(path, quiet=False):
         if not quiet:
             raise
         warnings.warn(f'tests may fail, unable to change the current working '
-                      f'directory to {path}: {exc}',
+                      f'directory to {path!r}: {exc}',
                       RuntimeWarning, stacklevel=3)
     try:
         yield os.getcwd()

Lib/test/test_support.py

@@ -158,7 +158,7 @@ class TestSupport(unittest.TestCase):
         self.assertEqual(len(warnings), 1, warnings)
         warn = warnings[0]
         self.assertTrue(warn.startswith(f'tests may fail, unable to create '
-                                        f'temporary directory {path}: '),
+                                        f'temporary directory {path!r}: '),
                         warn)
 
     # Tests for change_cwd()
@@ -204,7 +204,7 @@ class TestSupport(unittest.TestCase):
         warn = warnings[0]
         self.assertTrue(warn.startswith(f'tests may fail, unable to change '
                                         f'the current working directory '
-                                        f'to {bad_dir}: '),
+                                        f'to {bad_dir!r}: '),
                         warn)
 
     # Tests for change_cwd()
@@ -221,7 +221,7 @@ class TestSupport(unittest.TestCase):
         msg = messages[0]
         self.assertTrue(msg.startswith(f'tests may fail, unable to change '
                                        f'the current working directory '
-                                       f'to {path}: '),
+                                       f'to {path!r}: '),
                         msg)
 
     # Tests for temp_cwd()