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/parser.py b/Lib/email/parser.py
index 2fcaf25..782b985 100644
--- a/Lib/email/parser.py
+++ b/Lib/email/parser.py
@@ -7,7 +7,7 @@
__all__ = ['Parser', 'HeaderParser']
import warnings
-from cStringIO import StringIO
+from io import StringIO
from email.feedparser import FeedParser
from email.message import Message