Change some uses of cStringIO.StringIO to io.StringIO.
This is undoubtedly insufficient and in some cases just as broken as before.
diff --git a/Lib/csv.py b/Lib/csv.py
index 6ee12c8..758c79a 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -11,10 +11,7 @@
                  __doc__
 from _csv import Dialect as _Dialect
 
-try:
-    from cStringIO import StringIO
-except ImportError:
-    from StringIO import StringIO
+from io import StringIO
 
 __all__ = [ "QUOTE_MINIMAL", "QUOTE_ALL", "QUOTE_NONNUMERIC", "QUOTE_NONE",
             "Error", "Dialect", "excel", "excel_tab", "reader", "writer",