Revert "Merge pull request #13915 from edx/revert-13794-yro_implement-dateutil"

This reverts commit d59ab18b27, reversing
changes made to 0ebab35e89.

openedx/core/lib/tests/test_time_zone_utils.py

@@ -1,12 +1,10 @@
 """Tests covering time zone utilities."""
 from freezegun import freeze_time
 from student.tests.factories import UserFactory
-from openedx.core.djangoapps.user_api.preferences.api import set_user_preference
 from openedx.core.lib.time_zone_utils import (
     get_display_time_zone,
     get_time_zone_abbr,
     get_time_zone_offset,
-    get_user_time_zone,
 )
 from pytz import timezone, utc
 from unittest import TestCase
@@ -25,20 +23,6 @@ class TestTimeZoneUtils(TestCase):
         self.user = UserFactory.build()
         self.user.save()
 
-    def test_get_user_time_zone(self):
-        """
-        Test to ensure get_user_time_zone() returns the correct time zone
-        or UTC if user has not specified time zone.
-        """
-        # User time zone should be UTC when no time zone has been chosen
-        user_tz = get_user_time_zone(self.user)
-        self.assertEqual(user_tz, utc)
-
-        # User time zone should change when user specifies time zone
-        set_user_preference(self.user, 'time_zone', 'Asia/Tokyo')
-        user_tz = get_user_time_zone(self.user)
-        self.assertEqual(user_tz, timezone('Asia/Tokyo'))
-
     def _display_time_zone_helper(self, time_zone_string):
         """
         Helper function to return all info from get_display_time_zone()