[Core] Improve on_alert_tracker_error for lt >= 1.2

libtorrent 1.2 added endpoint struct to each tracker, to prevent false
updates we will need to verify that at least one endpoint to the errored
tracker is working.  if there is at least one working, it will not set
the tracker status to
error and set it to `Announce OK`. otherwise, it will use the error
message from the alert.

Refs: https://dev.deluge-torrent.org/ticket/3384

deluge/core/torrent.py

@@ -994,6 +994,8 @@ class Torrent(object):
                 call to get_status based on the session_id
             update (bool): If True the status will be updated from libtorrent
                 if False, the cached values will be returned
+            all_keys (bool): If True return all keys while ignoring the keys param
+                if False, return only the requested keys
 
         Returns:
             dict: a dictionary of the status keys and their values

deluge/core/torrentmanager.py

@@ -24,8 +24,15 @@ from twisted.internet.defer import Deferred, DeferredList
 from twisted.internet.task import LoopingCall
 
 import deluge.component as component
-from deluge._libtorrent import lt
-from deluge.common import PY2, archive_files, decode_bytes, get_magnet_info, is_magnet
+from deluge._libtorrent import LT_VERSION, lt
+from deluge.common import (
+    PY2,
+    VersionSplit,
+    archive_files,
+    decode_bytes,
+    get_magnet_info,
+    is_magnet,
+)
 from deluge.configmanager import ConfigManager, get_config_dir
 from deluge.core.authmanager import AUTH_LEVEL_ADMIN
 from deluge.core.torrent import Torrent, TorrentOptions, sanitize_filepath
@@ -1392,7 +1399,22 @@ class TorrentManager(component.Component):
         log.debug(
             'Tracker Error Alert: %s [%s]', decode_bytes(alert.message()), error_message
         )
-        torrent.set_tracker_status('Error: ' + error_message)
+        if VersionSplit(LT_VERSION) >= VersionSplit('1.2.0.0'):
+            # libtorrent 1.2 added endpoint struct to each tracker. to prevent false updates
+            # we will need to verify that at least one endpoint to the errored tracker is working
+            for tracker in torrent.handle.trackers():
+                if tracker['url'] == alert.url:
+                    if any(
+                        endpoint['last_error']['value'] == 0
+                        for endpoint in tracker['endpoints']
+                    ):
+                        torrent.set_tracker_status('Announce OK')
+                    else:
+                        torrent.set_tracker_status('Error: ' + error_message)
+                    break
+        else:
+            # preserve old functionality for libtorrent < 1.2
+            torrent.set_tracker_status('Error: ' + error_message)
 
     def on_alert_storage_moved(self, alert):
         """Alert handler for libtorrent storage_moved_alert"""