TIMESTAMP->dt: Use backports.zoneinfo on Python<3.9

docs/query.rst

@@ -291,7 +291,11 @@ Let's exercise all of them.
     >>> ccursor.fetchone()
     ['foo', datetime.datetime(2022, 7, 19, 4, 10, 36, 758000, tzinfo=<DstTzInfo 'Australia/Sydney' AEST+10:00:00 STD>)]
 
-    >>> import zoneinfo
+    >>> try:
+    ...     import zoneinfo
+    ... except ModuleNotFoundError:
+    ...     from backports import zoneinfo
+
     >>> ccursor.time_zone = zoneinfo.ZoneInfo("Australia/Sydney")
     >>> ccursor.execute("SELECT datetime_tz FROM locations ORDER BY name")
     >>> ccursor.fetchone()

setup.py

@@ -65,7 +65,8 @@ def read(path):
     },
     extras_require=dict(
         sqlalchemy=['sqlalchemy>=1.0,<1.5',
-                    'geojson>=2.5.0'],
+                    'geojson>=2.5.0',
+                    'backports.zoneinfo<1; python_version<"3.9"'],
         test=['tox>=3,<4',
               'zope.testing>=4,<5',
               'zope.testrunner>=5,<6',

src/crate/client/doctests/cursor.txt

@@ -415,11 +415,18 @@ Let's exercise all of them::
     >>> cursor.fetchone()
     ['foo', datetime.datetime(2022, 7, 19, 4, 10, 36, 758000, tzinfo=<DstTzInfo 'Australia/Sydney' AEST+10:00:00 STD>)]
 
-    >>> import zoneinfo
+    >>> try:
+    ...     import zoneinfo
+    ... except ModuleNotFoundError:
+    ...     from backports import zoneinfo
     >>> cursor.time_zone = zoneinfo.ZoneInfo("Australia/Sydney")
     >>> cursor.execute('')
-    >>> cursor.fetchone()
-    ['foo', datetime.datetime(2022, 7, 19, 4, 10, 36, 758000, tzinfo=zoneinfo.ZoneInfo(key='Australia/Sydney'))]
+    >>> record = cursor.fetchone()
+    >>> record
+    ['foo', datetime.datetime(2022, 7, 19, 4, 10, 36, 758000, ...zoneinfo.ZoneInfo(key='Australia/Sydney'))]
+
+    >>> record[1].tzname()
+    'AEST'
 
     >>> cursor.time_zone = "+0530"
     >>> cursor.execute('')

src/crate/client/test_cursor.py

@@ -20,10 +20,13 @@
 # software solely pursuant to the terms of the relevant commercial agreement.
 
 import datetime
-import zoneinfo
 from ipaddress import IPv4Address
 from unittest import TestCase
 from unittest.mock import MagicMock
+try:
+    import zoneinfo
+except ModuleNotFoundError:
+    from backports import zoneinfo
 
 import pytz