SF patch# 1770008 by Christian Heimes (plus some extras).
Completely get rid of StringIO.py and cStringIO.c.
I had to fix a few tests and modules beyond what Christian did, and
invent a few conventions. E.g. in elementtree, I chose to
write/return Unicode strings whe no encoding is given, but bytes when
an explicit encoding is given. Also mimetools was made to always
assume binary files.
diff --git a/Lib/email/mime/audio.py b/Lib/email/mime/audio.py
index c7290c4..f40bcbd 100644
--- a/Lib/email/mime/audio.py
+++ b/Lib/email/mime/audio.py
@@ -8,7 +8,7 @@
import sndhdr
-from cStringIO import StringIO
+from io import StringIO
from email import encoders
from email.mime.nonmultipart import MIMENonMultipart