`$COLUMNS` environment variable present in subprocess only when `env=None`

Bắt đầu với ví dụ subprocess.check_output tối thiểu và tái hiện cả bốn tổ hợp giữa thực thi tương tác và không tương tác, cùng env=None và env=os.environ. Theo dõi cách xử lý môi trường subprocess từ điểm vào đó; công việc được xem là hoàn tất khi hành vi khác nhau của COLUMNS được giải thích và được sửa hoặc được ghi tài liệu rõ ràng cùng với một bài kiểm thử tương ứng.

Bug report

for some reason which I cannot determine (perhaps a subtle difference between execvp and execvpe?) the $COLUMNS variable is mysteriously present in subprocesses when using env=None but not when using env=os.environ (which I expect to be identical in behaviour). this also seems to only happen with an interactive session?

here's a minimal case:

import sys, subprocess, os

subprocess.check_output(
    (sys.executable, '-c', 'import os; print(os.environ["COLUMNS"])'),
    # env=os.environ,
)

$ python3.11 -i t4.py
>>> 
$ python3.11 t4.py
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "<frozen os>", line 679, in __getitem__
KeyError: 'COLUMNS'
Traceback (most recent call last):
  File "/home/asottile/workspace/cpython/t4.py", line 3, in <module>
    subprocess.check_output(
  File "/usr/lib/python3.11/subprocess.py", line 466, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/subprocess.py", line 571, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '('/usr/bin/python3.11', '-c', 'import os; print(os.environ["COLUMNS"])')' returned non-zero exit status 1.

if I un-comment the line in the example script above -- it fails in both places:

$ sed -i 's/#//g' -- t4.py
$ python3.11 -i t4.py
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "<frozen os>", line 679, in __getitem__
KeyError: 'COLUMNS'
Traceback (most recent call last):
  File "/home/asottile/workspace/cpython/t4.py", line 3, in <module>
    subprocess.check_output(
  File "/usr/lib/python3.11/subprocess.py", line 466, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/subprocess.py", line 571, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '('/usr/bin/python3.11', '-c', 'import os; print(os.environ["COLUMNS"])')' returned non-zero exit status 1.
>>> 
$ python3.11 t4.py
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "<frozen os>", line 679, in __getitem__
KeyError: 'COLUMNS'
Traceback (most recent call last):
  File "/home/asottile/workspace/cpython/t4.py", line 3, in <module>
    subprocess.check_output(
  File "/usr/lib/python3.11/subprocess.py", line 466, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/subprocess.py", line 571, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '('/usr/bin/python3.11', '-c', 'import os; print(os.environ["COLUMNS"])')' returned non-zero exit status 1.

normally $COLUMNS is a shell variable and not an environment variable, but that doesn't really explain where it's coming from and why it's different depending both on interactiveness and on env= parameter:

Your environment

• CPython versions tested on: 3.12a3, 3.11.1, 3.10.6
• Operating system and architecture: ubuntu 22.04, x86_64 -- I also tried in docker and it reproduces there as well -- kernel is 5.15.0-56-generic