allow the first call to wcsxfrm to return ERANGE

If the output buffer provided to wcsxfrm is too small, errno is set to ERANGE. We should not error out in that case.

Author: benjaminp

Modules/_localemodule.c

@@ -263,10 +263,11 @@ PyLocale_strxfrm(PyObject* self, PyObject* args)
     errno = 0;
     n2 = wcsxfrm(buf, s, n1);
     if (errno) {
-        PyErr_SetFromErrno(PyExc_OSError);
-        goto exit;
-    }
-    if (n2 >= (size_t)n1) {
+        if (errno != ERANGE) {
+            PyErr_SetFromErrno(PyExc_OSError);
+            goto exit;
+        }
+        assert(n2 >= (size_t)n1);
         /* more space needed */
         wchar_t * new_buf = PyMem_Realloc(buf, (n2+1)*sizeof(wchar_t));
         if (!new_buf) {