fix: replace deprecated datetime.utcfromtimestamp()/utcnow() calls (#268)

Both APIs are deprecated since Python 3.12 and scheduled for removal.

- aprsd/packets/core.py: datetime.utcfromtimestamp(ts)
    -> datetime.fromtimestamp(ts, tz=timezone.utc)

- aprsd/plugins/time.py: pytz.datetime.datetime.utcnow()
    -> datetime.now(timezone.utc).replace(tzinfo=None)
  (naive UTC returned to preserve pytz.utc.localize() contract)

- tests/plugins/test_time.py: same fix in test setup

Closes #249

ChangeLog.md

@@ -16,6 +16,8 @@ Generated by [`auto-changelog`](https://github.com/CookPete/auto-changelog).
 
 - Fix RingBuffer mutable class-level 'data: list = []' default — move to __init__ instance attribute [`aa43f60`](https://github.com/craigerl/aprsd/commit/aa43f60)
 
+- Fix deprecated datetime.utcfromtimestamp()/utcnow() calls — replace with timezone-aware equivalents [`e7b0a19`](https://github.com/craigerl/aprsd/commit/e7b0a19)
+
 - Add reset() to @singleton decorator; update tests to use ClassName.reset() instead of ClassName.instance = None [`ef19aaa`](https://github.com/craigerl/aprsd/commit/ef19aaa)
 
 - Fix PacketTrack.keys/items/values — return list snapshots instead of live dict views outside the lock [`088436e`](https://github.com/craigerl/aprsd/commit/088436e)

aprsd/packets/core.py

@@ -2,7 +2,7 @@ import logging
 import re
 import time
 from dataclasses import dataclass, field
-from datetime import datetime
+from datetime import datetime, timezone
 
 # Due to a failure in python 3.8
 from typing import Any, List, Optional, Type, TypeVar, Union
@@ -316,7 +316,9 @@ class GPSPacket(Packet):
     def _build_time_zulu(self):
         """Build the timestamp in UTC/zulu."""
         if self.timestamp:
-            return datetime.utcfromtimestamp(self.timestamp).strftime('%d%H%M')
+            return datetime.fromtimestamp(self.timestamp, tz=timezone.utc).strftime(
+                '%d%H%M'
+            )
 
     def _build_payload(self):
         """The payload is the non headers portion of the packet."""

aprsd/plugins/time.py

@@ -24,7 +24,9 @@ class TimePlugin(plugin.APRSDRegexCommandPluginBase):
         return pytz.timezone(str(lz))
 
     def _get_utcnow(self):
-        return pytz.datetime.datetime.utcnow()
+        import datetime as _dt
+
+        return _dt.datetime.now(_dt.timezone.utc).replace(tzinfo=None)
 
     def build_date_str(self, localzone):
         utcnow = self._get_utcnow()

tests/plugins/test_time.py

@@ -1,3 +1,4 @@
+import datetime as _dt
 from unittest import mock
 
 import pytz
@@ -15,7 +16,7 @@ class TestTimePlugins(test_plugin.TestPlugin):
     @mock.patch('aprsd.plugins.time.TimePlugin._get_local_tz')
     @mock.patch('aprsd.plugins.time.TimePlugin._get_utcnow')
     def test_time(self, mock_utcnow, mock_localtz):
-        utcnow = pytz.datetime.datetime.utcnow()
+        utcnow = _dt.datetime.now(_dt.timezone.utc).replace(tzinfo=None)
         mock_utcnow.return_value = utcnow
         tz = pytz.timezone('US/Pacific')
         mock_localtz.return_value = tz