gh-91928: Add `datetime.UTC` alias for `datetime.timezone.utc` (GH-91973)

### fixes #91928

`UTC` is now module attribute aliased to `datetime.timezone.utc`.
You can now do the following:
```python
from datetime import UTC
```

2 files changed, 9 insertions, 3 deletions

diff --git a/Lib/datetime.py b/Lib/datetime.py
index 260b1de..7f79aa4 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -5,7 +5,7 @@ time zone and DST data sources.
 """
 
 __all__ = ("date", "datetime", "time", "timedelta", "timezone", "tzinfo",
-           "MINYEAR", "MAXYEAR")
+           "MINYEAR", "MAXYEAR", "UTC")
 
 
 import time as _time
@@ -2290,7 +2290,8 @@ class timezone(tzinfo):
             return f'UTC{sign}{hours:02d}:{minutes:02d}:{seconds:02d}'
         return f'UTC{sign}{hours:02d}:{minutes:02d}'
 
-timezone.utc = timezone._create(timedelta(0))
+UTC = timezone.utc = timezone._create(timedelta(0))
+
 # bpo-37642: These attributes are rounded to the nearest minute for backwards
 # compatibility, even though the constructor will accept a wider range of
 # values. This may change in the future.
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 335cded..d85b546 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -28,6 +28,7 @@ from datetime import timedelta
 from datetime import tzinfo
 from datetime import time
 from datetime import timezone
+from datetime import UTC
 from datetime import date, datetime
 import time as _time
 
@@ -66,6 +67,9 @@ class TestModule(unittest.TestCase):
         self.assertEqual(datetime.MINYEAR, 1)
         self.assertEqual(datetime.MAXYEAR, 9999)
 
+    def test_utc_alias(self):
+        self.assertIs(UTC, timezone.utc)
+
     def test_all(self):
         """Test that __all__ only points to valid attributes."""
         all_attrs = dir(datetime_module)
@@ -81,7 +85,7 @@ class TestModule(unittest.TestCase):
                     if not name.startswith('__') and not name.endswith('__'))
         allowed = set(['MAXYEAR', 'MINYEAR', 'date', 'datetime',
                        'datetime_CAPI', 'time', 'timedelta', 'timezone',
-                       'tzinfo', 'sys'])
+                       'tzinfo', 'UTC', 'sys'])
         self.assertEqual(names - allowed, set([]))
 
     def test_divide_and_round(self):
@@ -310,6 +314,7 @@ class TestTimeZone(unittest.TestCase):
 
     def test_tzname(self):
         self.assertEqual('UTC', timezone.utc.tzname(None))
+        self.assertEqual('UTC', UTC.tzname(None))
         self.assertEqual('UTC', timezone(ZERO).tzname(None))
         self.assertEqual('UTC-05:00', timezone(-5 * HOUR).tzname(None))
         self.assertEqual('UTC+09:30', timezone(9.5 * HOUR).tzname(None))