Test failure in test_executemany_server_failure_during_writes

从 tests/test_execute.py 开始，重点查看第 215 行失败的断言附近的 TestExecuteMany.test_executemany_server_failure_during_writes。使用 Python 3.12、PostgreSQL 15.4 和 asyncio 重现测试，然后将观察到的 128 的位置与测试预期的提前停止进行比较。完成的标准是理解该失败，并且测试能够稳定通过，同时不添加没有充分依据的平台特定 skip。

• asyncpg version: 0.29.0
• PostgreSQL version: 15.4
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: N/A, building the python-asyncpg package on Fedora Linux infrastructure
• Python version: 3.12.0
• Platform: Fedora Linux Rawhide, s390x architecture (only!)
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: No, I am the maintainer of the distribution package.
• If you built asyncpg locally, which version of Cython did you use?: 0.29.35
• Can the issue be reproduced under both asyncio and
  uvloop?: No, only asyncio. yes

This is new in 0.29.0. I don’t have any idea why it is happening.

I can’t reproduce this with PYTHONASYNCIODEBUG=1, nor can I reproduce it with USE_UVLOOP=1. I have now seen this on x86_64 with asyncio and PYTHONASYNCIODEBUG=1.

I don’t have interactive access to an s390x machine, but I am happy to run experiments or test proposed fixes by submitting package test builds on Fedora infrastructure. For the time being, I plan to simply skip this test on s390x.

=================================== FAILURES ===================================
________ TestExecuteMany.test_executemany_server_failure_during_writes _________
Traceback (most recent call last):
  File "/usr/lib64/python3.12/unittest/case.py", line 58, in testPartExecutor
    yield
  File "/usr/lib64/python3.12/unittest/case.py", line 634, in run
    self._callTestMethod(testMethod)
  File "/usr/lib64/python3.12/unittest/case.py", line 589, in _callTestMethod
    if method() is not None:
       ^^^^^^^^
  File "/builddir/build/BUILDROOT/python-asyncpg-0.29.0-1.fc40.s390x/usr/lib64/python3.12/site-packages/asyncpg/_testbase/__init__.py", line 92, in wrapper
    self.loop.run_until_complete(coro)
  File "/usr/lib64/python3.12/asyncio/base_events.py", line 664, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/asyncpg-0.29.0/tests/test_execute.py", line 215, in test_executemany_server_failure_during_writes
    self.assertLess(pos, 128, 'should stop early')
  File "/usr/lib64/python3.12/unittest/case.py", line 1257, in assertLess
    self.fail(self._formatMessage(msg, standardMsg))
  File "/usr/lib64/python3.12/unittest/case.py", line 715, in fail
    raise self.failureException(msg)
AssertionError: 128 not less than 128 : should stop early