The streamreader in utf_8_sig.py fails when asked to read a specified 
bytelength of data that ends up in the middle of a multibyte utf8 code.

I will attached a atandalone unittest (which does work from autotest, but 
doesn't use test_support), test_utf8sig_stream.py.

I will attach a patch (applied to the trunk 2.6 version), u8sig26.diff.

Regards,
..jim

Oops, it looks like my patch may have broken test_partial in test_codecs. I 
will try to figure out what the test_partial does in the next day or so, 
unless someone else can add some insignt in the meantime.

.jim

One additional clue: test_codecs succeeds in verbose mode but fails in non-
verbose mode (autotest "verbosity") .. I think. My eyes are getting 
blurry. More tomorrow, I guess.

..j

I found the errror in my previous patch. It lacked a self.decode=.. line 
in the StreamReader.decode elif branch. 

I attach a replacement patch diff-u.py26_utf8sig (apply to the 2.6 version 
of utf_8_sig.py. (If allowed, I will next remove the incorrect patch.)

This one passes test_codecs.py as well as my previously attached test 
module.

The resulting utf_8_sig.py may benefit from further refctoring, but I 
didn't want to do more than necessary to fix the immediate bug.

Regards,
..jim

Checked in your change and the test as r59049 (trunk) and r59050 (2.5).
Thanks for the patch.