Remove two unneeded imports in 'io'.

Lib/io.py

@@ -59,10 +59,8 @@ __all__ = ["BlockingIOError", "open", "IOBase", "RawIOBase", "FileIO",
 
 import os
 import abc
-import sys
 import codecs
 import _fileio
-import warnings
 import threading
 
 # open() uses st_blksize whenever we can

Misc/NEWS

@@ -48,6 +48,8 @@ Core and Builtins
 Library
 -------
 
+- Remove unneeded imports of 'sys' and 'warnings' from 'io'.
+
 - Remove unneeded imports of 'warnings' from shelve, filecmp, and dummy_thread.
 
 - Issue #3575: Incremental decoder's decode function now takes bytearray