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 ptyz 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] 7d9fda625fd5e16c91a9b95920c477f857193389

Change-Id: Ica344021a4e922bcfd20d20cffcce585a5742c8f

oslo_utils/timeutils.py

@@ -22,10 +22,16 @@ import datetime
 import functools
 import logging
 import time
-import zoneinfo
 
 import iso8601
 
+try:
+    import zoneinfo
+except ImportError:
+    # zoneinfo is available in Python >= 3.9
+    import pytz
+    zoneinfo = None
+
 from oslo_utils import reflection
 
 # ISO 8601 extended time format with microseconds
@@ -225,8 +231,14 @@ 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 = zoneinfo.ZoneInfo(tzname)
-        dt = dt.replace(tzinfo=tzinfo)
+
+        if zoneinfo:
+            tzinfo = zoneinfo.ZoneInfo(tzname)
+            dt = dt.replace(tzinfo=tzinfo)
+        else:
+            tzinfo = pytz.timezone(tzname)
+            dt = tzinfo.localize(dt)
+
     return dt
 
 

releasenotes/notes/implement-zoneinfo-to-remove-pytz-fba6f70db09ecdb8.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

@@ -5,6 +5,7 @@
 
 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