How to use the tzlocal.unix._try_tz_from_env function in tzlocal

tz_local = tzlocal.unix._tz_from_env(
            ':' + os.path.join(self.path, 'test_data', 'Harare'))
        self.assertEqual(tz_local.zone, 'local')
        # Make sure the local timezone is the same as the Harare one above.
        # We test this with a past date, so that we don't run into future changes
        # of the Harare timezone.
        dt = datetime(2012, 1, 1, 5)
        self.assertEqual(tz_harare.localize(dt), tz_local.localize(dt))

        # Non-zoneinfo timezones are not supported in the TZ environment.
        self.assertRaises(pytz.UnknownTimeZoneError, tzlocal.unix._tz_from_env,
                          'GMT+03:00')

        # Test the _try function
        os.environ['TZ'] = 'Africa/Harare'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertEqual(tz_harare.zone, 'Africa/Harare')
        # With a zone that doesn't exist
        os.environ['TZ'] = 'Just Nonsense'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertIsNone(tz_harare)

self.assertEqual(tz_harare.zone, 'Africa/Harare')

        tz_local = tzlocal.unix._tz_from_env(':' + os.path.join(self.path, 'test_data', 'Harare'))
        self.assertEqual(tz_local.zone, 'local')
        # Make sure the local timezone is the same as the Harare one above.
        # We test this with a past date, so that we don't run into future changes
        # of the Harare timezone.
        dt = datetime(2012, 1, 1, 5)
        self.assertEqual(tz_harare.localize(dt), tz_local.localize(dt))

        # Non-zoneinfo timezones are not supported in the TZ environment.
        self.assertRaises(pytz.UnknownTimeZoneError, tzlocal.unix._tz_from_env, 'GMT+03:00')

        # Test the _try function
        os.environ['TZ'] = 'Africa/Harare'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertEqual(tz_harare.zone, 'Africa/Harare')
        # With a zone that doesn't exist
        os.environ['TZ'] = 'Just Nonsense'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertIsNone(tz_harare)

# Make sure the local timezone is the same as the Harare one above.
        # We test this with a past date, so that we don't run into future changes
        # of the Harare timezone.
        dt = datetime(2012, 1, 1, 5)
        self.assertEqual(tz_harare.localize(dt), tz_local.localize(dt))

        # Non-zoneinfo timezones are not supported in the TZ environment.
        self.assertRaises(pytz.UnknownTimeZoneError, tzlocal.unix._tz_from_env, 'GMT+03:00')

        # Test the _try function
        os.environ['TZ'] = 'Africa/Harare'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertEqual(tz_harare.zone, 'Africa/Harare')
        # With a zone that doesn't exist
        os.environ['TZ'] = 'Just Nonsense'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertIsNone(tz_harare)

self.assertEqual(tz_harare.zone, 'Africa/Harare')

        tz_local = tzlocal.unix._tz_from_env(':' + os.path.join(self.path, 'test_data', 'Harare'))
        self.assertEqual(tz_local.zone, 'local')
        # Make sure the local timezone is the same as the Harare one above.
        # We test this with a past date, so that we don't run into future changes
        # of the Harare timezone.
        dt = datetime(2012, 1, 1, 5)
        self.assertEqual(tz_harare.localize(dt), tz_local.localize(dt))

        # Non-zoneinfo timezones are not supported in the TZ environment.
        self.assertRaises(pytz.UnknownTimeZoneError, tzlocal.unix._tz_from_env, 'GMT+03:00')

        # Test the _try function
        os.environ['TZ'] = 'Africa/Harare'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertEqual(tz_harare.zone, 'Africa/Harare')
        # With a zone that doesn't exist
        os.environ['TZ'] = 'Just Nonsense'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertIsNone(tz_harare)

# We test this with a past date, so that we don't run into future changes
        # of the Harare timezone.
        dt = datetime(2012, 1, 1, 5)
        self.assertEqual(tz_harare.localize(dt), tz_local.localize(dt))

        # Non-zoneinfo timezones are not supported in the TZ environment.
        self.assertRaises(pytz.UnknownTimeZoneError, tzlocal.unix._tz_from_env,
                          'GMT+03:00')

        # Test the _try function
        os.environ['TZ'] = 'Africa/Harare'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertEqual(tz_harare.zone, 'Africa/Harare')
        # With a zone that doesn't exist
        os.environ['TZ'] = 'Just Nonsense'
        tz_harare = tzlocal.unix._try_tz_from_env()
        self.assertIsNone(tz_harare)