fix: migrate datetime.utcnow for python 3.12 (#1413)

Author: arithmetic1728

google/auth/_helpers.py

@@ -92,7 +92,14 @@ def utcnow():
     Returns:
         datetime: The current time in UTC.
     """
-    return datetime.datetime.utcnow()
+    # We used datetime.utcnow() before, since it's deprecated from python 3.12,
+    # we are using datetime.now(timezone.utc) now. "utcnow()" is offset-native
+    # (no timezone info), but "now()" is offset-aware (with timezone info).
+    # This will cause datetime comparison problem. For backward compatibility,
+    # we need to remove the timezone info.
+    now = datetime.datetime.now(datetime.timezone.utc)
+    now = now.replace(tzinfo=None)
+    return now
 
 
 def datetime_to_secs(value):

tests/test_credentials.py

@@ -55,17 +55,15 @@ def test_expired_and_valid():
     # Set the expiration to one second more than now plus the clock skew
     # accomodation. These credentials should be valid.
     credentials.expiry = (
-        datetime.datetime.utcnow()
-        + _helpers.REFRESH_THRESHOLD
-        + datetime.timedelta(seconds=1)
+        _helpers.utcnow() + _helpers.REFRESH_THRESHOLD + datetime.timedelta(seconds=1)
     )
 
     assert credentials.valid
     assert not credentials.expired
 
     # Set the credentials expiration to now. Because of the clock skew
     # accomodation, these credentials should report as expired.
-    credentials.expiry = datetime.datetime.utcnow()
+    credentials.expiry = _helpers.utcnow()
 
     assert not credentials.valid
     assert credentials.expired

tests_async/test_credentials_async.py

@@ -46,17 +46,15 @@ def test_expired_and_valid():
     # Set the expiration to one second more than now plus the clock skew
     # accomodation. These credentials should be valid.
     credentials.expiry = (
-        datetime.datetime.utcnow()
-        + _helpers.REFRESH_THRESHOLD
-        + datetime.timedelta(seconds=1)
+        _helpers.utcnow() + _helpers.REFRESH_THRESHOLD + datetime.timedelta(seconds=1)
     )
 
     assert credentials.valid
     assert not credentials.expired
 
     # Set the credentials expiration to now. Because of the clock skew
     # accomodation, these credentials should report as expired.
-    credentials.expiry = datetime.datetime.utcnow()
+    credentials.expiry = _helpers.utcnow()
 
     assert not credentials.valid
     assert credentials.expired