From b7f136e73eda63c4bef46d2a749faf3692cddc5c Mon Sep 17 00:00:00 2001
From: Guido van Rossum <guido@python.org>
Date: Wed, 22 Aug 2007 18:14:10 +0000
Subject: Make IOBase (and hence all other classes in io.py) use ABCMeta as its
 metaclass, so you can use their class .register() method to register virtual
 subclasses.

---
 Lib/io.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Lib/io.py b/Lib/io.py
index 40ea687..40c2186 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -31,6 +31,7 @@ __all__ = ["BlockingIOError", "open", "IOBase", "RawIOBase", "FileIO",
            "BufferedRandom", "TextIOBase", "TextIOWrapper"]
 
 import os
+import abc
 import sys
 import codecs
 import _fileio
@@ -178,7 +179,7 @@ class UnsupportedOperation(ValueError, IOError):
     pass
 
 
-class IOBase:
+class IOBase(metaclass=abc.ABCMeta):
 
     """Base class for all I/O classes.
 
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