RSS: Add support for feed attributes in template string

See https://feedparser.readthedocs.io/en/latest/common-rss-elements.html#accessing-common-channel-elements

plugins/RSS/config.py

@@ -68,7 +68,9 @@ conf.registerChannelValue(RSS, 'format',
     will use for displaying headlines of a RSS feed that is triggered
     manually. In addition to fields defined by feedparser ($published
     (the entry date), $title, $link, $description, $id, etc.), the following
-    variables can be used: $feed_name, $date (parsed date, as defined in
+    variables can be used: $feed_name (the configured name)
+    $feed_title/$feed_subtitle/$feed_author/$feed_language/$feed_link,
+    $date (parsed date, as defined in
     supybot.reply.format.time)""")))
 conf.registerChannelValue(RSS, 'announceFormat',
     registry.String(_('News from $feed_name: $title <$link>'),

plugins/RSS/plugin.py

@@ -493,10 +493,11 @@ class RSS(callbacks.Plugin):
             template = self.registryValue(key_name, channel, network)
         date = entry.get('published_parsed')
         date = utils.str.timestamp(date)
-        s = string.Template(template).safe_substitute(
-                entry,
-                feed_name=feed.name,
-                date=date)
+        kwargs = {"feed_%s" % k: v for (k, v) in feed.data.items() if
+                  isinstance(v, str)}
+        kwargs["feed_name"] = feed.name
+        kwargs.update(entry)
+        s = string.Template(template).safe_substitute(entry, **kwargs, date=date)
         return self._normalize_entry(s)
 
     def announce_entry(self, irc, channel, feed, entry):

plugins/RSS/test.py

@@ -359,6 +359,14 @@ class RSSTestCase(ChannelPluginTestCase):
             self.assertRegexp('rss http://xkcd.com/rss.xml',
                     'On the other hand, the refractor\'s')
 
+    @mock_urllib
+    def testFeedAttribute(self, mock):
+        timeFastForward(1.1)
+        with conf.supybot.plugins.RSS.format.context('$feed_title: $title'):
+            mock._data = xkcd_new
+            self.assertRegexp('rss http://xkcd.com/rss.xml',
+                              r'xkcd\.com: Telescopes')
+
     @mock_urllib
     def testBadlyFormedFeedWithNoItems(self, mock):
         # This combination will cause the RSS command to show the last parser