Solaris 10's id(1M) does not support the "-G" option, so we get the following:

% ./python -m test test_posix 
[1/1] test_posix
id: illegal option -- G
Usage: id [-ap] [user]
1 test OK.

The code already tests that id -G (std) output, and assumes that id -G is not supported if the output is empty. 

QUESTION: Does the user compiling the code need to see the stderr output of id? After all the test is correctly skipped.

Fix:
% diff ./Lib/test/test_posix.py.FCS ./Lib/test/test_posix.py
378c378
<         with os.popen('id -G') as idg:
---
>         with os.popen('id -G 2> /dev/null') as idg:

Consideration: Lib/platform.py has introduced DEV_NULL but it does not seem to be used in other code or tests (beside platform.py).

Regards,

Peter