datetime: Use timedatectl to get list of time zones

Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/modules/datetime/forms.py

@@ -21,18 +21,21 @@ Forms for configuring date and time
 
 from django import forms
 from django.utils.translation import ugettext_lazy as _
-import glob
-import re
+import logging
+import subprocess
 
 from plinth.forms import ServiceForm
 
 
+logger = logging.getLogger(__name__)
+
+
 class DateTimeForm(ServiceForm):
     """Date/time configuration form."""
     time_zone = forms.ChoiceField(
         label=_('Time Zone'),
         help_text=_('Set your time zone to get accurate timestamps. \
-This will set the systemwide time zone.'))
+This will set the system-wide time zone.'))
 
     def __init__(self, *args, **kwargs):
         """Initialize the date/time form."""
@@ -48,23 +51,14 @@ This will set the systemwide time zone.'))
 
     @staticmethod
     def get_time_zones():
-        """Return list of available time zones"""
-        time_zones = []
-        for line in open('/usr/share/zoneinfo/zone.tab'):
-            if re.match(r'^(#|\s*$)', line):
-                continue
+        """Return the list time zones."""
+        command = ['timedatectl', 'list-timezones']
+        try:
+            process = subprocess.run(command, stdout=subprocess.PIPE,
+                                     check=True)
+        except subprocess.CalledProcessError as exception:
+            logger.exception('Error getting time zones: %s', exception)
+            return []
 
-            try:
-                time_zones.append(line.split()[2])
-            except IndexError:
-                pass
-
-        time_zones.sort()
-
-        additional_time_zones = [
-            path[len('/usr/share/zoneinfo/'):]
-            for path in glob.glob('/usr/share/zoneinfo/Etc/*')]
-
-        # Add additional time zones at the top to make them more
-        # noticeable because people won't look for them
-        return additional_time_zones + time_zones
+        output = process.stdout.decode()
+        return output.splitlines()