non-deterministic test_channel test failure

Hi,

On Guix, building using Python 3.11.4 and the following dependencies:

python-hatch-vcs@0.5.0 python-hatchling@1.27.0 python-pytest-bootstrap@8.4.1

I encountered:

FAILED testing/test_channel.py::TestChannelBasicBehaviour::test_channel_passing_over_channel[main_thread_only-popen] - execnet.gateway_base.RemoteError: Traceback (most recent call last):
  File "/gnu/store/n9wcfy3gx8gk3dd2s4xgc5119ylykcha-python-execnet-2.1.1/lib/python3.11/site-packages/execnet/gateway_base.py", line 1291, in executetask
    exec(co, loc)
  File "<remote exec>", line 2, in <module>
AssertionError
= 1 failed, 465 passed, 614 skipped, 4 xfailed, 11 xpassed, 1 warning in 59.96s =

This was under high load, and it seems difficult to retrigger that same failure (I've just built the package/ran the test suite for 5 times without the problem being triggered).

从 testing/test_channel.py 和 TestChannelBasicBehaviour::test_channel_passing_over_channel 开始，重点关注 main_thread_only-popen 情况及其远程 AssertionError。在高负载下重现该故障并检查 channel 传递行为；当测试在所报告的环境中不再出现非确定性失败时，即视为完成。