Merge pull request cherrypy#1992 from chiatchiat/utc-time-in-LazyRfc3…

…339UtcTime

This patch fixes `LazyRfc3339UtcTime` to return correct time using
the UTC timezone. Previously, it mistakenly used the local timezone
value for the RFC 3339 representation.

cherrypy/_cplogging.py

@@ -452,6 +452,6 @@ def emit(self, record):
 
 class LazyRfc3339UtcTime(object):
     def __str__(self):
-        """Return now() in RFC3339 UTC Format."""
-        now = datetime.datetime.now()
-        return now.isoformat('T') + 'Z'
+        """Return utcnow() in RFC3339 UTC Format."""
+        iso_formatted_now = datetime.datetime.utcnow().isoformat('T')
+        return f'{iso_formatted_now!s}Z'

cherrypy/test/test_logging.py

@@ -1,5 +1,6 @@
 """Basic tests for the CherryPy core: request handling."""
 
+import datetime
 import logging
 
 from cheroot.test import webtest
@@ -197,6 +198,33 @@ def test_custom_log_format(log_tracker, monkeypatch, server):
     )
 
 
+def test_utc_in_timez(monkeypatch):
+    """Test that ``LazyRfc3339UtcTime`` is rendered as ``str`` using UTC timestamp."""
+    utcoffset8_local_time_in_naive_utc = (
+        datetime.datetime(
+            year=2020,
+            month=1,
+            day=1,
+            hour=1,
+            minute=23,
+            second=45,
+            tzinfo=datetime.timezone(datetime.timedelta(hours=8)),
+        )
+        .astimezone(datetime.timezone.utc)
+        .replace(tzinfo=None)
+    )
+
+    class mock_datetime:
+        @classmethod
+        def utcnow(cls):
+            return utcoffset8_local_time_in_naive_utc
+
+    monkeypatch.setattr('datetime.datetime', mock_datetime)
+    rfc3339_utc_time = str(cherrypy._cplogging.LazyRfc3339UtcTime())
+    expected_time = '2019-12-31T17:23:45Z'
+    assert rfc3339_utc_time == expected_time
+
+
 def test_timez_log_format(log_tracker, monkeypatch, server):
     """Test a customized access_log_format string, which is a
     feature of _cplogging.LogManager.access()."""