Clean up test based off pr suggestions

Lib/test/test_site.py

@@ -467,40 +467,26 @@ def test_sitecustomize_executed(self):
 
     @support.requires_subprocess()
     def test_customization_modules_on_startup(self):
-        # Check that sitecustomize and or usercustomize are executed on startup
-        mod_info = [
-            # func to get directory, file base name
-            ('getsitepackages', 'sitecustomize')
+        mod_names = [
+            'sitecustomize'
         ]
 
         if site.ENABLE_USER_SITE:
-            mod_info.append(('getusersitepackages', 'usercustomize'),)
+            mod_names.append('usercustomize')
 
-        for func_name, module_name in mod_info:
-            # getusersitepackages returns a string.. getsitepackages returns a list..
-            # handle either way.
-            base_path = getattr(site, func_name)()
-            if not isinstance(base_path, str):
-                base_path = base_path[0]
+        temp_dir = tempfile.mkdtemp()
+        self.addCleanup(os_helper.rmtree, temp_dir)
 
-            try:
-                os.makedirs(base_path, exist_ok=True)
-            except PermissionError:
-                # Can't modify system site packages depending on the system configuration
-                continue
+        with EnvironmentVarGuard() as environ:
+            environ['PYTHONPATH'] = temp_dir
 
-            customize_path = os.path.join(base_path, f'{module_name}.py')
-            if os.path.exists(customize_path):
-                # backup old sitecustomize.py
-                oldcustomize_path = customize_path + '.old'
-                if os.path.exists(oldcustomize_path):
-                    os.remove(oldcustomize_path)
-                os.rename(customize_path, oldcustomize_path)
-                self.addCleanup(os.rename, oldcustomize_path, customize_path)
+            for module_name in mod_names:
+                os_helper.rmtree(temp_dir)
+                os.mkdir(temp_dir)
 
-            eyecatcher = f'EXECUTED_{module_name}'
+                customize_path = os.path.join(temp_dir, f'{module_name}.py')
+                eyecatcher = f'EXECUTED_{module_name}'
 
-            try:
                 with open(customize_path, 'w') as f:
                     f.write(f'print("{eyecatcher}")')
 
@@ -515,8 +501,7 @@ def test_customization_modules_on_startup(self):
                 if 'usercustomize' == module_name:
                     output = subprocess.check_output([sys.executable, '-s', '-c', '""'])
                     self.assertNotIn(eyecatcher, output.decode('utf-8'))
-            finally:
-                os.remove(customize_path)
+
 
     @unittest.skipUnless(hasattr(urllib.request, "HTTPSHandler"),
                          'need SSL support to download license')