Inconsistant behavior of .readable() and .writable() on io.IOBase

Bug report

The methods .readble() and .writable() on io.IOBase should return a boolean representing if the file can be read from/written to. However, calling .readable() on a closed IO file object causes a ValueError, whereas calling .writable() on a closed file returns False if the file was opened with just read permissions, but raises ValueError if it was opened with read and write permissions.

Make a folder with a text file in, then run:

f = open("hello.txt")
print(f.writable())
print(f.readable())
f.close()
print(f.writable())
print(f.readable())

This will output:

False
True
False
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file

Then doing a similar thing, but with w+ permissions

f = open("hello.txt", "w+")
print(f.writable())
print(f.readable())
f.close()
print(f.writable())
print(f.readable())

Will output

True
True
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file

Your environment

• CPython versions tested on: 3.10.4
• Operating system and architecture: Windows 64bit

Start by reproducing the two closed-file examples in the issue, then inspect the io.IOBase.readable() and writable() entry points and their related tests. Done means the two methods have consistent, documented behavior for closed files while preserving the expected results for open files.