fix DeprecationWarning with datetime.utcnow() (#86)

This is not the same as
#71, but it
originates at the same point. When I updated pytz to 2023.3.post1, I
started getting:
```
E       DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
```
This fixes it.

---------

Co-authored-by: Samuel Colvin <[email protected]>

.github/workflows/ci.yml

@@ -59,7 +59,7 @@ jobs:
 
     - uses: actions/setup-python@v4
       with:
-        python-version: '3.10'
+        python-version: '3.11'
 
     - run: pip install -r requirements/linting.txt
 

dirty_equals/_datetime.py

@@ -184,7 +184,13 @@ def _get_now(self) -> datetime:
         if self.tz is None:
             return datetime.now()
         else:
-            return datetime.utcnow().replace(tzinfo=timezone.utc).astimezone(self.tz)
+            try:
+                from datetime import UTC
+
+                utc_now = datetime.now(UTC).replace(tzinfo=timezone.utc)
+            except ImportError:
+                utc_now = datetime.utcnow().replace(tzinfo=timezone.utc)
+            return utc_now.astimezone(self.tz)
 
     def prepare(self, other: Any) -> datetime:
         # update approx for every comparing, to check if other value is dirty equal

tests/test_datetime.py

@@ -99,7 +99,13 @@ def test_repr():
 
 
 def test_is_now_tz():
-    now_ny = datetime.utcnow().replace(tzinfo=timezone.utc).astimezone(pytz.timezone('America/New_York'))
+    try:
+        from datetime import UTC
+
+        utc_now = datetime.now(UTC).replace(tzinfo=timezone.utc)
+    except ImportError:
+        utc_now = datetime.utcnow().replace(tzinfo=timezone.utc)
+    now_ny = utc_now.astimezone(pytz.timezone('America/New_York'))
     assert now_ny == IsNow(tz='America/New_York')
     # depends on the time of year and DST
     assert now_ny == IsNow(tz=timezone(timedelta(hours=-5))) | IsNow(tz=timezone(timedelta(hours=-4)))
@@ -111,7 +117,6 @@ def test_is_now_tz():
     assert now.isoformat() == IsNow(iso_string=True)
     assert now.isoformat() != IsNow
 
-    utc_now = datetime.utcnow().replace(tzinfo=timezone.utc)
     assert utc_now == IsNow(tz=timezone.utc)