bpo-39184: Fix incorrect return value (GH-18580)

https://bugs.python.org/issue39184

Automerge-Triggered-By: @zooba
(cherry picked from commit 6c444d0dab)

Co-authored-by: Steve Dower <steve.dower@python.org>

PC/msvcrtmodule.c

@@ -180,7 +180,7 @@ msvcrt_open_osfhandle_impl(PyObject *module, void *handle, int flags)
     int fd;
 
     if (PySys_Audit("msvcrt.open_osfhandle", "Ki", handle, flags) < 0) {
-        return NULL;
+        return -1;
     }
 
     _Py_BEGIN_SUPPRESS_IPH