Fix compatibility with Python 3.8

We removed compatibility with Python 3.8 once but it was added back to
tested runtimes for 2023.2. Thus we have to make sure the code works
with Python 3.8, which was broken by [1].

Note that pytz is added back to requirmenets.txt and is now required
regardless of the python version. This is a short term solution until
we figure out the way to fix the requirement-check job (or we again
remove python 3.8 support).

[1] a326ec5eea86d7458953a229b4dbd887595f68f1

Change-Id: I3b222bb59260dff7a06a5ed48720df3dc8c74ea7

oslo_serialization/msgpackutils.py

@@ -33,9 +33,16 @@ import functools
 import itertools
 import uuid
 from xmlrpc import client as xmlrpclib
-import zoneinfo
 
 import msgpack
+
+try:
+    import zoneinfo
+except ImportError:
+    # zoneinfo is available in Python >= 3.9
+    from pytz import timezone
+    zoneinfo = None
+
 from oslo_utils import importutils
 
 netaddr = importutils.try_import("netaddr")
@@ -236,7 +243,10 @@ class DateTimeHandler(object):
             'microsecond': dt.microsecond,
         }
         if dt.tzinfo:
-            tz = str(dt.tzinfo)
+            if zoneinfo:
+                tz = str(dt.tzinfo)
+            else:
+                tz = dt.tzinfo.tzname(None)
             dct['tz'] = tz
         return dumps(dct, registry=self._registry)
 
@@ -264,8 +274,12 @@ class DateTimeHandler(object):
                                second=dct['second'],
                                microsecond=dct['microsecond'])
         if 'tz' in dct and dct['tz']:
-            tzinfo = zoneinfo.ZoneInfo(dct['tz'])
-            dt = dt.replace(tzinfo=tzinfo)
+            if zoneinfo:
+                tzinfo = zoneinfo.ZoneInfo(dct['tz'])
+                dt = dt.replace(tzinfo=tzinfo)
+            else:
+                tzinfo = timezone(dct['tz'])
+                dt = tzinfo.localize(dt)
         return dt
 
 

oslo_serialization/tests/test_msgpackutils.py

@@ -15,11 +15,17 @@
 import datetime
 import itertools
 from xmlrpc import client as xmlrpclib
-import zoneinfo
 
 import netaddr
 from oslotest import base as test_base
 
+try:
+    import zoneinfo
+except ImportError:
+    # zoneinfo is available in Python >= 3.9
+    from pytz import timezone
+    zoneinfo = None
+
 from oslo_serialization import msgpackutils
 from oslo_utils import uuidutils
 
@@ -145,22 +151,31 @@ class MsgPackUtilsTest(test_base.BaseTestCase):
         self.assertEqual(today, _dumps_loads(today))
 
     def test_datetime_tz_clone(self):
-        eastern = zoneinfo.ZoneInfo('US/Eastern')
         now = datetime.datetime.now()
-        e_dt = now.replace(tzinfo=eastern)
+        if zoneinfo:
+            eastern = zoneinfo.ZoneInfo('US/Eastern')
+            e_dt = now.replace(tzinfo=eastern)
+        else:
+            eastern = timezone('US/Eastern')
+            e_dt = eastern.localize(now)
         e_dt2 = _dumps_loads(e_dt)
         self.assertEqual(e_dt, e_dt2)
         self.assertEqual(e_dt.strftime(_TZ_FMT), e_dt2.strftime(_TZ_FMT))
 
     def test_datetime_tz_different(self):
-        eastern = zoneinfo.ZoneInfo('US/Eastern')
-        pacific = zoneinfo.ZoneInfo('US/Pacific')
         now = datetime.datetime.now()
-
-        now = now.replace(tzinfo=eastern)
-        e_dt = now
-        now = now.replace(tzinfo=pacific)
-        p_dt = now
+        if zoneinfo:
+            eastern = zoneinfo.ZoneInfo('US/Eastern')
+            pacific = zoneinfo.ZoneInfo('US/Pacific')
+            now = now.replace(tzinfo=eastern)
+            e_dt = now
+            now = now.replace(tzinfo=pacific)
+            p_dt = now
+        else:
+            eastern = timezone('US/Eastern')
+            pacific = timezone('US/Pacific')
+            e_dt = eastern.localize(now)
+            p_dt = pacific.localize(now)
 
         self.assertNotEqual(e_dt, p_dt)
         self.assertNotEqual(e_dt.strftime(_TZ_FMT), p_dt.strftime(_TZ_FMT))

releasenotes/notes/implement-zoneinfo-to-remove-pytz-c136b33bbfbfe59f.yaml

@@ -1,6 +1,5 @@
 ---
 other:
   - |
-    Implement zoneinfo to allow us to remove pytz's dependency. zoneinfo
-    was introduced by python 3.9, and the series 2023.2 (bobcat) set py39
-    as the minimal supported runtime, so we are able to remove pytz.
+    Implement zoneinfo to allow us to remove pytz's dependency for Python 3.9
+    and 3.10

requirements.txt

@@ -10,4 +10,5 @@
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 msgpack>=0.5.2 # Apache-2.0
 oslo.utils>=3.33.0 # Apache-2.0
+pytz>=2013.6 # MIT
 tzdata>=2022.4 # MIT