Check whether a string resize is necessary at the end
of PyString_DecodeEscape(). This prevents a call to
_PyString_Resize() for the empty string, which would
result in a PyErr_BadInternalCall(), because the
empty string has more than one reference.

This closes SF bug http://www.python.org/sf/603937
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 0362d26..36cebd5 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -23,9 +23,16 @@
         f = reader(s)
         self.assertEquals(f.read(), u"spamspam")
 
+class EscapeDecodeTest(unittest.TestCase):
+    def test_empty_escape_decode(self):
+        self.assertEquals(codecs.escape_decode(""), ("", 0))
+
 
 def test_main():
-    test_support.run_unittest(UTF16Test)
+    suite = unittest.TestSuite()
+    suite.addTest(unittest.makeSuite(UTF16Test))
+    suite.addTest(unittest.makeSuite(EscapeDecodeTest))
+    test_support.run_suite(suite)
 
 
 if __name__ == "__main__":