Make os.get_terminal_size check isatty before calling ioctl

[mhsmith]

On Android, stdout is probably not connected, and calling ioctl(TIOCGWINSZ) on an invalid file descriptor causes a log message "avc: denied { ioctl }", and returns EACCES. This still meets the specification of get_terminal_size, which only says it throws an OSError.

However, the log noise can be a problem. You can see it in this run of the CPython test suite, mostly in tests that involve argparse, such as test_ast. Some common tools such as pytest are even worse affected, as they call get_terminal_size very often.

So this PR adds an isatty check before caling ioctl. This should be harmless on other platforms, so I haven't made it Android-specific.

This isn't a bugfix, so it shouldn't be backported.

[mhsmith]

Confirmed that the relevant test is skipped on Android:

0:00:00 [1/1] test_os.test_os
test_does_not_crash (test.test_os.test_os.TermsizeTests.test_does_not_crash)
Check if get_terminal_size() returns a meaningful value. ... skipped 'failed to query terminal size'
test_stty_match (test.test_os.test_os.TermsizeTests.test_stty_match)
Check if stty returns the same results ... skipped 'requires subprocess support'
test_windows_fd (test.test_os.test_os.TermsizeTests.test_windows_fd)
Check if get_terminal_size() returns a meaningful value in Windows ... skipped 'Windows specific test'
 
----------------------------------------------------------------------
Ran 3 tests in 0.000s
 
OK (skipped=3)

And still passes on macOS:

0:00:00 load avg: 1.90 mem: 23.8 MiB [1/1] test_os.test_os
test_does_not_crash (test.test_os.test_os.TermsizeTests.test_does_not_crash)
Check if get_terminal_size() returns a meaningful value. ... ok
test_stty_match (test.test_os.test_os.TermsizeTests.test_stty_match)
Check if stty returns the same results ... ok
test_windows_fd (test.test_os.test_os.TermsizeTests.test_windows_fd)
Check if get_terminal_size() returns a meaningful value in Windows ... skipped 'Windows specific test'

----------------------------------------------------------------------
Ran 3 tests in 0.011s

OK (skipped=1)

% ./cross-build/build/python.exe -c 'import os; print(os.get_terminal_size())'
os.terminal_size(columns=193, lines=63

[freakboy3742]

Makes sense to me 👍

Agreed that this doesn't meet the requirements for a backport to stable releases; but I've back ported to 3.15 because it will be an appreciable quality-of-life improvement, and 3.15 isn't final yet.

[miss-islington-app]

Thanks @mhsmith for the PR, and @freakboy3742 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

[bedevere-app]

GH-154903 is a backport of this pull request to the 3.15 branch.