Unicode objects are currently taken as binary data by the write()
method.  This is not what Unicode users expect, nor what the
StringIO.py code does.  Until somebody adds a way to specify binary or
text mode for cStringIO objects, change the format string to use "t#"
instead of "s#", so that it will request the "text buffer" version.
This will try the default encoding for Unicode objects.

This is *not* a 2.2 bugfix (since it *is* a semantic change).