Improve code readability and consistency

This commit:

- Changes to Python 3 template string rather than the formatted string
  syntax.
- Calls the Deluge API once per plugin run for the "states" mode, rather
  than once per torrent. Lines of code are reduced. The readability is
  improved too, since the API call is similar to how the "peers" mode
  works.
- Updates the label for the "state" entry "paused" to match it's name in the
  libtorrent API: "stopped". "Queued" is split into "Queued seeding" and
  "Queued downloads" to match the libtorrent API too.

plugins/torrent/deluge_

@@ -73,8 +73,8 @@ Each of them has "payload" and "overhead" value.
 
 =head2 states
 
-In the "states" mode, this plugin shows the number of torrents in each state :
-Downloading, Seeding, Paused, Error, Queued, Checking, Other
+In the "states" mode, this plugin shows the number of torrents in the states:
+Seeding, Uploading, Downloading, Checking, Stopped, Queued seeding, Queued downloads, Errors
 
 =head1 MAGIC MARKERS
 
@@ -128,29 +128,6 @@ conf = {
     'password': os.getenv('password', '')
 }
 
-names_for_munin = {
-    'numConnections': 'numConnections',
-    'payloadUploadRate': 'payloadUploadRate',
-    'overheadUploadRate': 'overheadUploadRate',
-    'payloadDownloadRate': 'payloadDownloadRate',
-    'overheadDownloadRate': 'overheadDownloadRate',
-    'state.Seeding': 'seeding',
-    'state.Downloading': 'downloading',
-    'state.Paused': 'paused',
-    'state.Error': 'error',
-    'state.Queued': 'queued',
-    'state.Checking': 'checking',
-    'state.Other': 'other',
-}
-
-torrent_states = ["Downloading",
-                  "Seeding",
-                  "Paused",
-                  "Error",
-                  "Queued",
-                  "Checking",
-                  "Other"]
-
 modes = ["bandwidth", "peers", "states"]
 
 connection_keys = [
@@ -160,6 +137,17 @@ connection_keys = [
     { 'id': 'peer.num_peers_down_interested', 'label': 'Interested (download)' }
 ]
 
+torrent_keys = [
+    { 'id': 'ses.num_seeding_torrents', 'label': 'Seeding' },
+    { 'id': 'ses.num_upload_only_torrents', 'label': 'Uploading' },
+    { 'id': 'ses.num_downloading_torrents', 'label': 'Downloading' },
+    { 'id': 'ses.num_checking_torrents', 'label': 'Checking' },
+    { 'id': 'ses.num_stopped_torrents', 'label': 'Stopped' },
+    { 'id': 'ses.num_queued_seeding_torrents', 'label': 'Queued seeding' },
+    { 'id': 'ses.num_queued_download_torrents', 'label': 'Queued downloads' },
+    { 'id': 'ses.num_error_torrents', 'label': 'Error' },
+]
+
 def for_munin(value):
     return value.replace('.', '').replace('_', '')
 
@@ -217,8 +205,11 @@ class StatClient:
                 errbackArgs=("get_session_status failed"))
         elif self.mode == "states":
             log.debug("Calling get_session_state")
-            client.core.get_session_state().addCallbacks(
-                self.on_session_state,
+            keys = []
+            for torrent_key in torrent_keys:
+                keys.append(torrent_key['id'])
+            client.core.get_session_status(keys=keys).addCallbacks(
+                self.on_torrent_session_state,
                 self.end_session,
                 errbackArgs=("get_session_state failed"))
         else:
@@ -244,55 +235,20 @@ class StatClient:
         payload_upload_rate = values['payload_upload_rate']
         overhead_upload_rate = upload_rate - payload_upload_rate
 
-        print("{0}.value {1}".format(
-            names_for_munin["payloadDownloadRate"], payload_download_rate))
-        print("{0}.value {1}".format(
-            names_for_munin["overheadDownloadRate"], overhead_download_rate))
-        print("{0}.value {1}".format(
-            names_for_munin["payloadUploadRate"], payload_upload_rate))
-        print("{0}.value {1}".format(
-            names_for_munin["overheadUploadRate"], overhead_upload_rate))
+        print(f"payloadDownloadRate.value {payload_download_rate}")
+        print(f"overheadDownloadRate.value {overhead_download_rate}")
+        print(f"payloadUploadRate.value {payload_upload_rate}")
+        print(f"overheadUploadRate.value {overhead_upload_rate}")
         self.end_session("Done")
 
-    def on_session_state(self, torrent_ids):
-        log.debug("Got session state from the daemon")
-
-        self.states = {}
-        for state_name in torrent_states:
-            self.states[state_name] = 0
-
-        deferred_list = []
-        for torrent_id in torrent_ids:
-            log.debug(" - TorrentId : %s", torrent_id)
-            d = client.core.get_torrent_status(torrent_id, ['state'])
-            d.addCallback(self.on_one_torrent_info, torrent_id)
-            d.addErrback(self.on_one_torrent_info_failed, torrent_id)
-            deferred_list.append(d)
-
-        defer.DeferredList(deferred_list).addCallback(
-            self.on_all_torrent_info_fetched)
-
-    def on_one_torrent_info_failed(self, torrent_id):
-        log.debug("Failed fetching torrent info %s", torrent_id)
-        self.state["Error"] = self.state["Error"] + 1
-
-    def on_one_torrent_info(self, value, torrent_id):
-        log.debug("Got torrent info : %s -> %s", torrent_id, value)
-        state = value.get("state", "Error")
-
-        if state not in self.states:
-            log.warn("State '%s' is unknown !", state)
-            state = "Other"
-
-        self.states[state] += 1
-
-    def on_all_torrent_info_fetched(self, res):
-        log.debug("on_all_torrent_info_fetched : %s", self.states)
-
-        for state in self.states:
-            print("{0}.value {1}".format(
-                names_for_munin["state." + state], self.states[state]))
+    def on_torrent_session_state(self, result):
+        log.debug("Got torrent session state from the daemon", result)
 
+        for torrent_key in torrent_keys:
+            print(
+                f"{for_munin(torrent_key['id'])}.value "
+                f"{result[torrent_key['id']]}"
+            )
         self.end_session("Done")
 
 
@@ -359,12 +315,7 @@ def print_config(mode):
         print("overheadUploadRate.info Bandwidth 'lost' due to overhead while downloading and "
               "uploading torrents")
     elif mode == "states":
-        print("graph_title Torrents states")
-
-        graph_order = " ".join(
-            [names_for_munin["state.{}".format(name)] for name in torrent_states])
-
-        print("graph_order " + graph_order)
+        print("graph_title Torrent states")
         print("graph_args --base 1000 -r --lower-limit 0")
         print("graph_vlabel number of torrents")
         print("graph_scale yes")
@@ -372,13 +323,11 @@ def print_config(mode):
         print("graph_category filetransfer")
         print("graph_period second")
 
-        for state_name in torrent_states:
-            print(names_for_munin["state." + state_name] + ".label " + state_name)
-            print(names_for_munin["state." + state_name] + ".draw AREASTACK")
-            print(names_for_munin["state." + state_name] + ".type GAUGE")
-            print(names_for_munin["state." + state_name] + ".min 0")
-            print(names_for_munin["state." + state_name]
-                  + ".info Number of torrents in the '" + state_name + "' state")
+        for torrent_key in torrent_keys:
+            print(f"{for_munin(torrent_key['id'])}.label {torrent_key['label']}")
+            print(f"{for_munin(torrent_key['id'])}.min 0")
+            print(f"{for_munin(torrent_key['id'])}.draw AREASTACK")
+            print(f"{for_munin(torrent_key['id'])}.type GAUGE")
 
 
 def fetch_info(mode):
@@ -407,8 +356,7 @@ if len(sys.argv) > 1:
             print(mode)
         sys.exit(0)
     elif action == "version":
-        print('Deluge Torrent Munin plugin, version {0}'.format(
-            plugin_version))
+        print(f"Deluge Torrent Munin plugin, version {plugin_version}")
         sys.exit(0)
     elif action:
         log.warn("Unknown argument '%s'", action)