Deprecate pytz and use zoneinfo (#1680)

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* remove unused noqa

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* re-add import

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* use pytest-freezer (#1683)

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Asif Saif Uddin <auvipy@gmail.com>

kombu/asynchronous/timer.py

@@ -16,10 +16,10 @@ from vine.utils import wraps
 
 from kombu.log import get_logger
 
-try:
-    from pytz import utc
-except ImportError:  # pragma: no cover
-    utc = None
+if sys.version_info >= (3, 9):
+    from zoneinfo import ZoneInfo
+else:
+    from backports.zoneinfo import ZoneInfo
 
 if TYPE_CHECKING:
     from types import TracebackType
@@ -29,13 +29,13 @@ __all__ = ('Entry', 'Timer', 'to_timestamp')
 logger = get_logger(__name__)
 
 DEFAULT_MAX_INTERVAL = 2
-EPOCH = datetime.utcfromtimestamp(0).replace(tzinfo=utc)
+EPOCH = datetime.utcfromtimestamp(0).replace(tzinfo=ZoneInfo("UTC"))
 IS_PYPY = hasattr(sys, 'pypy_version_info')
 
 scheduled = namedtuple('scheduled', ('eta', 'priority', 'entry'))
 
 
-def to_timestamp(d, default_timezone=utc, time=monotonic):
+def to_timestamp(d, default_timezone=ZoneInfo("UTC"), time=monotonic):
     """Convert datetime to timestamp.
 
     If d' is already a timestamp, then that will be used.

requirements/test.txt

@@ -1,6 +1,6 @@
-pytz
 pytest>=7.1.1
 pytest-sugar
 Pyro4
 hypothesis
 pytest-freezer
+backports.zoneinfo>=0.2.1; python_version < '3.9'

t/unit/utils/test_json.py

@@ -1,18 +1,23 @@
 from __future__ import annotations
 
+import sys
 import uuid
 from collections import namedtuple
 from datetime import datetime
 from decimal import Decimal
 
 import pytest
-import pytz
 from hypothesis import given, settings
 from hypothesis import strategies as st
 
 from kombu.utils.encoding import str_to_bytes
 from kombu.utils.json import dumps, loads
 
+if sys.version_info >= (3, 9):
+    from zoneinfo import ZoneInfo
+else:
+    from backports.zoneinfo import ZoneInfo
+
 
 class Custom:
 
@@ -27,7 +32,7 @@ class test_JSONEncoder:
     @pytest.mark.freeze_time("2015-10-21")
     def test_datetime(self):
         now = datetime.utcnow()
-        now_utc = now.replace(tzinfo=pytz.utc)
+        now_utc = now.replace(tzinfo=ZoneInfo("UTC"))
 
         original = {
             'datetime': now,