Remove _IOBase check to support writable objects

Author: ptim0626

Lib/argparse.py

@@ -86,7 +86,6 @@
 ]
 
 
-import io as _io
 import os as _os
 import re as _re
 import sys as _sys
@@ -2890,8 +2889,6 @@ def _print_message(self, message, file=None):
             return
         if file is None:
             file = _sys.stderr
-        elif not isinstance(file, _io.IOBase):
-            raise ValueError(f"invalid file object {file}")
         if file is not None:
             file.write(message)
 

Lib/test/test_argparse.py

@@ -85,7 +85,7 @@ def test_invalid_file_only(self):
             for invalid_f in ("invalid file", "", 0):
                 with (
                     self.subTest(func=func, invalid_f=invalid_f),
-                    self.assertRaises(ValueError),
+                    self.assertRaises(AttributeError),
                 ):
                     func(file=invalid_f)