The Windows buildbots are currently broken due to a codec issue. I populated the "nosy" list based on the "unicode" experts from the Experts Index.

http://buildbot.python.org/all/builders/AMD64%20Windows7%20SP1%203.x/builds/4040

test_streamreaderwriter (test.test_codecs.WithStmtTest) ... test test_codecs failed
ok

======================================================================
ERROR: test_readline (test.test_codecs.CP65001Test)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_codecs.py", line 157, in test_readline
    self.assertEqual(readalllines("".join(vw), True), "|".join(vw))
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_codecs.py", line 136, in readalllines
    line = reader.readline(size=size, keepends=keepends)
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\codecs.py", line 548, in readline
    data = self.read(readsize, firstline=True)
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\codecs.py", line 494, in read
    newchars, decodedbytes = self.decode(data, self.errors)
UnicodeDecodeError: 'CP_UTF8' codec can't decode bytes in position 0--1: No mapping for the Unicode character exists in the target code page.

Note that this appears to be in Windows-specific code ("CP_UTF8"), rather than being cross-platform code which happens to only fail on Windows. So we need someone who does both Windows and Unicode.

It looks to be related to changeset e988661e458c5402c0236cd1084a8671249a760d
Issue bpo-20538: UTF-7 incremental decoder produced inconsistant string when
input was truncated in BASE64 section.

Serhiy said on IRC that he doesn't have a Windows development environment, so he didn't think he could help.

UTF-7 decoder is not related to this test.

The test_readline test was broken from the born, and a part of this test was do nothing. After fixing it in bpo-20520, new bugs were exposed: bpo-20538 and this. This bug was hidden until fixing bpo-20538.

Note that there is no test_partial in CP65001Test. Perhaps it is related.

The simplest solution would be to temporary skip test_readline in CP65001Test:

    test_readline = unittest.expectedFailure(ReadTest.test_readline)

The test tries to decode a partial UTF-8 bytes string. The problem is that codecs.code_page_decode() doesn't implement fully partial decoders. The decoder only supports partial decoding for a few code pages: 932, 936, 949, 950, and 1361. The partial decoding is currently based on IsDBCSLeadByteEx():
http://msdn.microsoft.com/en-us/library/windows/desktop/dd318667%28v=vs.85%29.aspx

It may be possible to enhance decoders, but it's not a regression from Python 3.3 and so can be done in Python 3.5.

Please just skip failing tests for CP_UTF8 (cp 65001) and maybe other Windows code pages in test_codecs.

(I don't have time to write a patch to skip, sorry.)

New changeset 4f6499fc2f09 by Victor Stinner in branch 'default':
Issue bpo-20571: skip test_readline() of test_codecs for Windows code page 65001.
http://hg.python.org/cpython/rev/4f6499fc2f09

I opened bpo-20574 to implement the missing feature for cp65001.

New changeset d8f48717b74e by Victor Stinner in branch '3.3':
Issue bpo-20571: skip test_readline() of test_codecs for Windows code page 65001.
http://hg.python.org/cpython/rev/d8f48717b74e

Would have been nice to do this also on 3.3 branch...

Ah yes, sorry. I forgot that the utf-7 change was also applied to 3.3.