diff -r fb73fe5d0ab1 -r fffeff7721c0 Lib/test/test_urllib2.py
--- a/Lib/test/test_urllib2.py	Mon Nov 07 10:15:55 2011 +0000
+++ b/Lib/test/test_urllib2.py	Mon Nov 07 11:00:06 2011 -0500
@@ -1449,6 +1449,17 @@
         req = Request(url)
         self.assertEqual(req.get_full_url(), url)
 
+def test_HTTPError_interface():
+    """
+    Issue 13211 reveals that HTTPError didn't implement the URLError
+    interface even though HTTPError is a subclass of URLError.
+
+    >>> err = urllib.error.HTTPError(msg='something bad happened', url=None, code=None, hdrs=None, fp=None)
+    >>> assert hasattr(err, 'reason')
+    >>> err.reason
+    'something bad happened'
+    """
+
 def test_main(verbose=None):
     from test import test_urllib2
     support.run_doctest(test_urllib2, verbose)
diff -r fb73fe5d0ab1 -r fffeff7721c0 Lib/urllib/error.py
--- a/Lib/urllib/error.py	Mon Nov 07 10:15:55 2011 +0000
+++ b/Lib/urllib/error.py	Mon Nov 07 11:00:06 2011 -0500
@@ -55,6 +55,12 @@
     def __str__(self):
         return 'HTTP Error %s: %s' % (self.code, self.msg)
 
+    # since URLError specifies a .reason attribute, HTTPError should also
+    #  provide this attribute. See issue13211 for discussion.
+    @property
+    def reason(self):
+        return self.msg
+
 # exception raised when downloaded size does not match content-length
 class ContentTooShortError(URLError):
     def __init__(self, message, content):