# HG changeset patch
# Parent 8b3c609f3f73c90c4e1dd5a5b46b9a9df9d1dbcd

diff -r 8b3c609f3f73 Lib/test/test_exceptions.py
--- a/Lib/test/test_exceptions.py	Sun Jan 11 15:53:02 2015 -0500
+++ b/Lib/test/test_exceptions.py	Tue Jan 13 01:42:47 2015 +0000
@@ -6,6 +6,7 @@
 import pickle
 import weakref
 import errno
+import ctypes
 
 from test.support import (TESTFN, captured_output, check_impl_detail,
                           check_warnings, cpython_only, gc_collect, run_unittest,
@@ -245,6 +246,16 @@
             self.assertEqual(w.strerror, 'foo')
             self.assertEqual(w.filename, None)
 
+    def test_windows_message(self):
+        """Should fill in unknown error code in Windows error message"""
+        try:
+            windll = ctypes.windll
+        except AttributeError as err:
+            self.skipTest(err)
+        code = int.from_bytes(b"\xE0msc", "big")
+        self.assertRaisesRegex(OSError, format(code, "x"),
+            windll.kernel32.RaiseException, code, 0, 0, None)
+
     def testAttributes(self):
         # test that exception attributes are happy
 
diff -r 8b3c609f3f73 Python/errors.c
--- a/Python/errors.c	Sun Jan 11 15:53:02 2015 -0500
+++ b/Python/errors.c	Tue Jan 13 01:42:47 2015 +0000
@@ -491,7 +491,7 @@
                 /* Only ever seen this in out-of-mem
                    situations */
                 s_buf = NULL;
-                message = PyUnicode_FromFormat("Windows Error 0x%X", i);
+                message = PyUnicode_FromFormat("Windows Error 0x%x", i);
             } else {
                 /* remove trailing cr/lf and dots */
                 while (len > 0 && (s_buf[len-1] <= L' ' || s_buf[len-1] == L'.'))
@@ -600,7 +600,7 @@
         NULL);          /* no args */
     if (len==0) {
         /* Only seen this in out of mem situations */
-        message = PyUnicode_FromFormat("Windows Error 0x%X", err);
+        message = PyUnicode_FromFormat("Windows Error 0x%x", err);
         s_buf = NULL;
     } else {
         /* remove trailing cr/lf and dots */