Replace CUnicodeIO with StringIO

IPython/lib/pretty.py

@@ -83,12 +83,11 b' import types'
 import re
 import datetime
 from collections import deque
+from io import StringIO
 
 from IPython.utils.py3compat import PYPY, cast_unicode
 from IPython.utils.encoding import get_stream_enc
 
-from io import StringIO
-
 
 __all__ = ['pretty', 'pprint', 'PrettyPrinter', 'RepresentationPrinter',
     'for_type', 'for_type_by_name']
@@ -114,7 +113,7 b" def pretty(obj, verbose=False, max_width=79, newline='\\n', max_seq_length=MAX_SE"
     """
     Pretty print the object's representation.
     """
-    stream = CUnicodeIO()
+    stream = StringIO()
     printer = RepresentationPrinter(stream, verbose, max_width, newline, max_seq_length=max_seq_length)
     printer.pretty(obj)
     printer.flush()