Python 3.12: Deprecated utcnow and utcfromtimestamp

[pmisik]

Describe the incorrect behavior you saw
datetime.datetime.utcnow and datetime.datetime.utcfromtimestamp raise deprecation warnings in Python 3.12.

Describe how to cause this behavior

While running trial on buildbot this generates lots of deprecation warnings like:

Traceback (most recent call last):
  File "C:\P\twisted\src\twisted\logger\_observer.py", line 81, in __call__
    observer(event)
  File "C:\P\twisted\src\twisted\logger\_legacy.py", line 90, in __call__
    self.legacyObserver(event)
  File "C:\P\twisted\src\twisted\python\log.py", line 544, in emit
    timeStr = self.formatTime(eventDict["time"])
  File "C:\P\twisted\src\twisted\python\log.py", line 514, in formatTime
    tzOffset = -self.getTimezoneOffset(when)
  File "C:\P\twisted\src\twisted\python\log.py", line 493, in getTimezoneOffset
    offset = datetime.utcfromtimestamp(when) - datetime.fromtimestamp(when)
builtins.DeprecationWarning: datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.fromtimestamp(timestamp, datetime.UTC).
E           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Running buildbot trial with current HEAD & current trunk of twisted.

Describe the correct behavior you'd like to see
No deprecation warning reported while running trial under python 3.12.

Testing environment

• Operating System and Version; paste the output of these commands:

OS Name:                   Microsoft Windows 11 Home
OS Version:                10.0.22621 N/A Build 22621
OS Manufacturer:           Microsoft Corporation
OS Configuration:          Standalone Workstation
OS Build Type:             Multiprocessor Free
System Manufacturer:       Microsoft Corporation
BIOS Version:              Microsoft Corporation 15.11.140, 8. 7. 2022

• Twisted version
  22.10.0.post0
  a9ee8e5
• Reactor [e.g. select, iocp]
  twisted-iocpsupport 1.0.4

Additional context

• Deprecate utcnow and utcfromtimestamp Deprecate utcnow and utcfromtimestamp python/cpython#103857
• https://blog.ganssle.io/articles/2019/11/utcnow.html

[adiroiban]

Thanks for the report.

Happy to receive a PR with a fix for this :)

[adiroiban]

@pmisik not that until just now, twisted/twisted was not working/supported on 3.12

You can now try to install Twisted over git and see if this is still an issue. Thanks!