Move compatibility logic into its own module.

tempora/schedule.py

@@ -3,7 +3,7 @@
 
 For example, to run a job at 08:00 every morning in 'Asia/Calcutta':
 
->>> import zoneinfo
+>>> from tests.compat.py38 import zoneinfo
 >>> job = lambda: print("time is now", datetime.datetime())
 >>> time = datetime.time(8, tzinfo=zoneinfo.ZoneInfo('Asia/Calcutta'))
 >>> cmd = PeriodicCommandFixedDelay.daily_at(time, job)

tests/test_schedule.py

@@ -1,4 +1,3 @@
-import sys
 import time
 import random
 import datetime
@@ -9,10 +8,7 @@
 
 from tempora import schedule
 
-if sys.version_info >= (3, 9):
- from zoneinfo import ZoneInfo
-else: # pragma: no cover
- from backports.zoneinfo import ZoneInfo
+from .compat.py38 import zoneinfo
 
 
 do_nothing = type(None)
@@ -58,7 +54,7 @@ def test_command_at_noon(self):
  """
  Create a periodic command that's run at noon every day.
  """
- when = datetime.time(12, 0, tzinfo=ZoneInfo('UTC'))
+ when = datetime.time(12, 0, tzinfo=zoneinfo.ZoneInfo('UTC'))
  cmd = schedule.PeriodicCommandFixedDelay.daily_at(when, target=None)
  assert cmd.due() is False
  next_cmd = cmd.next()
@@ -80,13 +76,13 @@ def test_command_at_noon_distant_local(self, hour, tz_offset):
 
 class TestTimezones:
  def test_alternate_timezone_west(self):
- target_tz = ZoneInfo('US/Pacific')
+ target_tz = zoneinfo.ZoneInfo('US/Pacific')
  target = schedule.now().astimezone(target_tz)
  cmd = schedule.DelayedCommand.at_time(target, target=None)
  assert cmd.due()
 
  def test_alternate_timezone_east(self):
- target_tz = ZoneInfo('Europe/Amsterdam')
+ target_tz = zoneinfo.ZoneInfo('Europe/Amsterdam')
  target = schedule.now().astimezone(target_tz)
  cmd = schedule.DelayedCommand.at_time(target, target=None)
  assert cmd.due()
@@ -97,7 +93,7 @@ def test_daylight_savings(self):
  a DST boundary.
  """
  with freezegun.freeze_time('2018-03-10'):
- target_tz = ZoneInfo('US/Eastern')
+ target_tz = zoneinfo.ZoneInfo('US/Eastern')
  target_time = datetime.time(9, tzinfo=target_tz)
  cmd = schedule.PeriodicCommandFixedDelay.daily_at(
  target_time, target=lambda: None