fix: remove dependency on pytz (#472)

For googleapis/python-api-core#250

Fixes #468.

Author: busunkim96

google/cloud/pubsub_v1/subscriber/message.py

@@ -17,7 +17,6 @@
 import datetime as dt
 import json
 import math
-import pytz
 import time
 
 from google.cloud.pubsub_v1.subscriber._protocol import requests
@@ -110,7 +109,7 @@ def __init__(self, message, ack_id, delivery_attempt, request_queue):
         self._data = message.data
         self._publish_time = dt.datetime.fromtimestamp(
             message.publish_time.seconds + message.publish_time.nanos / 1e9,
-            tz=pytz.UTC,
+            tz=dt.timezone.utc,
         )
         self._ordering_key = message.ordering_key
         self._size = message.ByteSize()

tests/unit/pubsub_v1/subscriber/test_message.py

@@ -17,7 +17,6 @@
 import time
 
 import mock
-import pytz
 
 from google.api_core import datetime_helpers
 from google.cloud.pubsub_v1.subscriber import message
@@ -26,7 +25,7 @@
 from google.pubsub_v1 import types as gapic_types
 
 
-RECEIVED = datetime.datetime(2012, 4, 21, 15, 0, tzinfo=pytz.utc)
+RECEIVED = datetime.datetime(2012, 4, 21, 15, 0, tzinfo=datetime.timezone.utc)
 RECEIVED_SECONDS = datetime_helpers.to_milliseconds(RECEIVED) // 1000
 PUBLISHED_MICROS = 123456
 PUBLISHED = RECEIVED + datetime.timedelta(days=1, microseconds=PUBLISHED_MICROS)