fix: avoid rounding microsecond to 1_000_000

[dqkqd]

I'm using pytest with python 3.9, and my log-date-format is enabled for microseconds. However, my testsuite occasionally fails with the message below:

ValueError: microsecond must be in 0..999999

I'm pretty sure the issue occurred because we're rounding up microsecond here, which make it exceeds 999999.

pytest/src/_pytest/logging.py

Lines 72 to 75 in ac2cd72

	# Construct `datetime.datetime` object from `struct_time`
	# and msecs information from `record`
	dt = datetime(*ct[0:6], microsecond=round(record.msecs * 1000), tzinfo=tz)
	return dt.strftime(datefmt)

As we can see msecs can take more than 4 digits after decimal points, hence it can be rounded up to 1_000_000 after multiplying with 1_000. (in python 3.9)

>>> import logging
>>> r = logging.makeLogRecord({'msg': 'Message'})
>>> r.msecs
696.0451602935791

This is "fixed" in python 3.10 and 3.11 python/cpython#89047
They floored msecs so it will always never be rounded to 1_000_000.

>>> import logging
>>> r = logging.makeLogRecord({'msg': 'Message'})
>>> r.msecs
459.0

However, since we also support 3.8 and 3.9, I think we should fix this by flooring microsecond as well.
(I don't know how to write test for this case without mocking time.time())

[nicoddemus]

Other than my comment, could you please also add a changelog entry? Thanks!

[dqkqd]

Thanks for reviewing, I added comment and changelog.

[nicoddemus]

Thanks, appreciate it!