emails: Apply the user's hour format in login notification timestamps.

The timestamp used for new login notifications always used the 12-hour
format. Instead of that, we use now the one preferred by the user, as
reflected in their settings.

zerver/signals.py

@@ -79,7 +79,11 @@ def email_on_new_login(sender: Any, user: UserProfile, request: Any, **kwargs: A
         if user_tz == '':
             user_tz = timezone_get_current_timezone_name()
         local_time = timezone_now().astimezone(get_timezone(user_tz))
-        context['login_time'] = local_time.strftime('%A, %B %d, %Y at %I:%M%p %Z')
+        if user.twenty_four_hour_time:
+            hhmm_string = local_time.strftime('%H:%M')
+        else:
+            hhmm_string = local_time.strftime('%I:%M%p')
+        context['login_time'] = local_time.strftime('%A, %B %d, %Y at {} %Z'.format(hhmm_string))
         context['device_ip'] = request.META.get('REMOTE_ADDR') or _("Unknown IP address")
         context['device_os'] = get_device_os(user_agent)
         context['device_browser'] = get_device_browser(user_agent)

zerver/tests/test_new_users.py

@@ -30,6 +30,7 @@ class SendLoginEmailTest(ZulipTestCase):
 
             user = self.example_user('hamlet')
             user.timezone = 'US/Pacific'
+            user.twenty_four_hour_time = False
             user.date_joined = mock_time - datetime.timedelta(seconds=JUST_CREATED_THRESHOLD + 1)
             user.save()
             password = initial_password(user.email)
@@ -48,6 +49,17 @@ class SendLoginEmailTest(ZulipTestCase):
             # local time is correct and in email's body
             self.assertIn(reference_time, mail.outbox[0].body)
 
+            # Try again with the 24h time format setting enabled for this user
+            self.logout()  # We just logged in, we'd be redirected without this
+            user.twenty_four_hour_time = True
+            user.save()
+            with mock.patch('zerver.signals.timezone_now', return_value=mock_time):
+                self.client_post("/accounts/login/", info={"username": user.email, "password": password},
+                                 HTTP_USER_AGENT=firefox_windows)
+
+            reference_time = mock_time.astimezone(user_tz).strftime('%A, %B %d, %Y at %H:%M %Z')
+            self.assertIn(reference_time, mail.outbox[1].body)
+
     def test_dont_send_login_emails_if_send_login_emails_is_false(self) -> None:
         self.assertFalse(settings.SEND_LOGIN_EMAILS)
         email = self.example_email('hamlet')