The culprit:

diff -r b4e99bec0c8a Lib/test/test_codecs.py
--- a/Lib/test/test_codecs.py	Fri Feb 07 10:10:55 2014 +0200
+++ b/Lib/test/test_codecs.py	Fri Feb 07 17:14:12 2014 +0800
@@ -164,6 +164,8 @@
                 s = 10*(size*"a" + lineend + "xxx\n")
                 reader = getreader(s)
                 for i in range(10):
+                    if size==64 and self.encoding == 'utf-7' and lineend=='\u2028' and i == 3:
+                        import pdb; pdb.set_trace()
                     self.assertEqual(
                         reader.readline(keepends=True),
                         size*"a" + lineend,