From 7d9fda625fd5e16c91a9b95920c477f857193389 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Herv=C3=A9=20Beraud?= <hberaud@redhat.com>
Date: Tue, 7 Feb 2023 10:32:36 +0100
Subject: Implement zoneinfo support to drop dependency to pytz
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Zoneinfo was introduced within python 3.9.

The support of pytz will be removed within RHEL 10 [1].

2023.2 (bobcat) will move our testing runtime to py3.9 and py3.10
so we want to see pytz removed within this series.

tzdata is required at runtime in our gates, because, by default,
zoneinfo uses the system’s time zone data if available; if no system
time zone data is available, the library will fall back to using the
first-party tzdata package available on PyPI. Apparently our gates have no
time zone data available nor tzdata installed by default because we get the
following error without tzdata installed [3]:
`ModuleNotFoundError: No module named 'tzdata'

So I prefer to add tzdata in our requirements to avoid runtime failure
related to time zone and ensure that time zone are always available.

[1] https://issues.redhat.com/browse/RHEL-219
[2] https://review.opendev.org/c/openstack/governance/+/872232
[3] https://zuul.opendev.org/t/openstack/build/0a1576775e894b09bc31269fea00ba03/log/job-output.txt#1445`

Depends-on: https://review.opendev.org/c/openstack/requirements/+/875854
Change-Id: I1f88bdadc68bfa726eac1da1c5824c1ed352ad98
---
 oslo_utils/timeutils.py                                             | 6 +++---
 .../notes/implement-zoneinfo-to-remove-pytz-fba6f70db09ecdb8.yaml   | 6 ++++++
 requirements.txt                                                    | 2 +-
 3 files changed, 10 insertions(+), 4 deletions(-)
 create mode 100644 releasenotes/notes/implement-zoneinfo-to-remove-pytz-fba6f70db09ecdb8.yaml

diff --git a/oslo_utils/timeutils.py b/oslo_utils/timeutils.py
index 390be53..ba45fda 100644
--- a/oslo_utils/timeutils.py
+++ b/oslo_utils/timeutils.py
@@ -22,9 +22,9 @@ import datetime
 import functools
 import logging
 import time
+import zoneinfo
 
 import iso8601
-import pytz
 
 from oslo_utils import reflection
 
@@ -225,8 +225,8 @@ def unmarshall_time(tyme):
     if tzname:
         # Need to handle either iso8601 or python UTC format
         tzname = 'UTC' if tzname == 'UTC+00:00' else tzname
-        tzinfo = pytz.timezone(tzname)
-        dt = tzinfo.localize(dt)
+        tzinfo = zoneinfo.ZoneInfo(tzname)
+        dt = dt.replace(tzinfo=tzinfo)
     return dt
 
 
diff --git a/releasenotes/notes/implement-zoneinfo-to-remove-pytz-fba6f70db09ecdb8.yaml b/releasenotes/notes/implement-zoneinfo-to-remove-pytz-fba6f70db09ecdb8.yaml
new file mode 100644
index 0000000..24c7d7f
--- /dev/null
+++ b/releasenotes/notes/implement-zoneinfo-to-remove-pytz-fba6f70db09ecdb8.yaml
@@ -0,0 +1,6 @@
+---
+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.
diff --git a/requirements.txt b/requirements.txt
index 37374ac..9085e00 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,9 +5,9 @@
 
 iso8601>=0.1.11 # MIT
 oslo.i18n>=3.15.3 # Apache-2.0
-pytz>=2013.6 # MIT
 netaddr>=0.7.18 # BSD
 netifaces>=0.10.4 # MIT
 debtcollector>=1.2.0 # Apache-2.0
 pyparsing>=2.1.0 # MIT
 packaging>=20.4 # BSD
+tzdata>=2022.4 # MIT
-- 
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