This patch comes from upstream:

http://bugs.python.org/issue27369

--- a/Lib/test/test_pyexpat.py
+++ b/Lib/test/test_pyexpat.py
@@ -633,11 +633,9 @@ class MalformedInputTest(unittest.TestCa
         # \xc2\x85 is UTF-8 encoded U+0085 (NEXT LINE)
         xml = b"<?xml version\xc2\x85='1.0'?>\r\n"
         parser = expat.ParserCreate()
-        try:
+        err_pattern = r'XML declaration not well-formed: line 1, column \d+'
+        with self.assertRaisesRegex(expat.ExpatError, err_pattern):
             parser.Parse(xml, True)
-            self.fail()
-        except expat.ExpatError as e:
-            self.assertEqual(str(e), 'XML declaration not well-formed: line 1, column 14')
 
 class ErrorMessageTest(unittest.TestCase):
     def test_codes(self):