Remove opening/at-exit closing of devnull.

This was likely due to an issue on Python 2 seeing the date,
and does not seem useful anymore. Let's try to remove it.

Should close  #13896

IPython/utils/io.py

@@ -1,156 +1,151 b''
 # encoding: utf-8
 """
 IO related utilities.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 
 
 import atexit
 import os
 import sys
 import tempfile
 from pathlib import Path
 from warnings import warn
 
 from IPython.utils.decorators import undoc
 from .capture import CapturedIO, capture_output
 
-# setup stdin/stdout/stderr to sys.stdin/sys.stdout/sys.stderr
-devnull = open(os.devnull, "w", encoding="utf-8")
-atexit.register(devnull.close)
-
-
 class Tee(object):
     """A class to duplicate an output stream to stdout/err.
 
     This works in a manner very similar to the Unix 'tee' command.
 
     When the object is closed or deleted, it closes the original file given to
     it for duplication.
     """
     # Inspired by:
     # http://mail.python.org/pipermail/python-list/2007-May/442737.html
 
     def __init__(self, file_or_name, mode="w", channel='stdout'):
         """Construct a new Tee object.
 
         Parameters
         ----------
         file_or_name : filename or open filehandle (writable)
             File that will be duplicated
         mode : optional, valid mode for open().
             If a filename was give, open with this mode.
         channel : str, one of ['stdout', 'stderr']
         """
         if channel not in ['stdout', 'stderr']:
             raise ValueError('Invalid channel spec %s' % channel)
 
         if hasattr(file_or_name, 'write') and hasattr(file_or_name, 'seek'):
             self.file = file_or_name
         else:
             encoding = None if "b" in mode else "utf-8"
             self.file = open(file_or_name, mode, encoding=encoding)
         self.channel = channel
         self.ostream = getattr(sys, channel)
         setattr(sys, channel, self)
         self._closed = False
 
     def close(self):
         """Close the file and restore the channel."""
         self.flush()
         setattr(sys, self.channel, self.ostream)
         self.file.close()
         self._closed = True
 
     def write(self, data):
         """Write data to both channels."""
         self.file.write(data)
         self.ostream.write(data)
         self.ostream.flush()
 
     def flush(self):
         """Flush both channels."""
         self.file.flush()
         self.ostream.flush()
 
     def __del__(self):
         if not self._closed:
             self.close()
 
 
 def ask_yes_no(prompt, default=None, interrupt=None):
     """Asks a question and returns a boolean (y/n) answer.
 
     If default is given (one of 'y','n'), it is used if the user input is
     empty. If interrupt is given (one of 'y','n'), it is used if the user
     presses Ctrl-C. Otherwise the question is repeated until an answer is
     given.
 
     An EOF is treated as the default answer.  If there is no default, an
     exception is raised to prevent infinite loops.
 
     Valid answers are: y/yes/n/no (match is not case sensitive)."""
 
     answers = {'y':True,'n':False,'yes':True,'no':False}
     ans = None
     while ans not in answers.keys():
         try:
             ans = input(prompt+' ').lower()
             if not ans:  # response was an empty string
                 ans = default
         except KeyboardInterrupt:
             if interrupt:
                 ans = interrupt
             print("\r")
         except EOFError:
             if default in answers.keys():
                 ans = default
                 print()
             else:
                 raise
 
     return answers[ans]
 
 
 def temp_pyfile(src, ext='.py'):
     """Make a temporary python file, return filename and filehandle.
 
     Parameters
     ----------
     src : string or list of strings (no need for ending newlines if list)
         Source code to be written to the file.
     ext : optional, string
         Extension for the generated file.
 
     Returns
     -------
     (filename, open filehandle)
         It is the caller's responsibility to close the open file and unlink it.
     """
     fname = tempfile.mkstemp(ext)[1]
     with open(Path(fname), "w", encoding="utf-8") as f:
         f.write(src)
         f.flush()
     return fname
 
 
 @undoc
 def raw_print(*args, **kw):
     """DEPRECATED: Raw print to sys.__stdout__, otherwise identical interface to print()."""
     warn("IPython.utils.io.raw_print has been deprecated since IPython 7.0", DeprecationWarning, stacklevel=2)
 
     print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
           file=sys.__stdout__)
     sys.__stdout__.flush()
 
 @undoc
 def raw_print_err(*args, **kw):
     """DEPRECATED: Raw print to sys.__stderr__, otherwise identical interface to print()."""
     warn("IPython.utils.io.raw_print_err has been deprecated since IPython 7.0", DeprecationWarning, stacklevel=2)
 
     print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
           file=sys.__stderr__)
     sys.__stderr__.flush()