Issue #18180: Fix ref leak in _PyImport_GetDynLoadWindows().

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 3.3.3 release candidate 1?
 Core and Builtins
 -----------------
 
+- Issue #18180: Fix ref leak in _PyImport_GetDynLoadWindows().
+
 - Issue #18038: SyntaxError raised during compilation sources with illegal
   encoding now always contains an encoding name.
 

Python/dynload_win.c

@@ -262,8 +262,9 @@ dl_funcptr _PyImport_GetDynLoadWindows(const char *shortname,
                         theLength));
             }
             if (message != NULL) {
-                PyErr_SetImportError(message, PyUnicode_FromString(shortname),
-                                     pathname);
+                PyObject *shortname_obj = PyUnicode_FromString(shortname);
+                PyErr_SetImportError(message, shortname_obj, pathname);
+                Py_XDECREF(shortname_obj);
                 Py_DECREF(message);
             }
             return NULL;