Fix memory leak in path_converter()

Issue #28200: Replace PyUnicode_AsWideCharString() with
PyUnicode_AsUnicodeAndSize().

Misc/NEWS

@@ -29,6 +29,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #28200: Fix memory leak on Windows in the os module (fix
+  path_converter() function).
+
 - Issue #25400: RobotFileParser now correctly returns default values for
   crawl_delay and request_rate.  Initial patch by Peter Wirtz.
 

Modules/posixmodule.c

@@ -920,7 +920,7 @@ path_converter(PyObject *o, void *p)
 
     if (is_unicode) {
 #ifdef MS_WINDOWS
-        wide = PyUnicode_AsWideCharString(o, &length);
+        wide = PyUnicode_AsUnicodeAndSize(o, &length);
         if (!wide) {
             goto exit;
         }