fix escape_encode to return the correct consumed size
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 8caf018..f8563f6 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -835,6 +835,9 @@
         self.assertEquals(encoder(u"a")[1], 1)
         self.assertEquals(encoder(u"\xe9\u0142")[1], 2)
 
+        encoder = codecs.getencoder("string-escape")
+        self.assertEquals(encoder(r'\x00')[1], 4)
+
 # From http://www.gnu.org/software/libidn/draft-josefsson-idn-test-vectors.html
 nameprep_tests = [
     # 3.1 Map to nothing.