py3: Import StringIO from io

pyldap contributors · encukou · commit 8a54ae3c3396 · 2017-11-24T11:46:39.000+01:00
This was backported to Python 2.7. It uses the C-optimized version,
so cStringIO is not needed either.
diff --git a/Lib/ldif.py b/Lib/ldif.py
@@ -20,11 +20,7 @@
 
 import re
 from base64 import b64encode, b64decode
-
-try:
-  from cStringIO import StringIO
-except ImportError:
-  from StringIO import StringIO
+from io import StringIO
 
 from ldap.compat import urlparse, urlopen
 
