bot: respect priority field of plugins

edmond/bot.py

@@ -151,7 +151,9 @@ class Bot(irc.client.SimpleIRCClient, Logger):
     def run_plugin_callbacks(self, event):
         """Run appropriate callbacks for each plugin."""
         etype = event.type
-        for plugin in filter(lambda p: p.is_ready, self.plugins):
+        plugins = filter(lambda p: p.is_ready, self.plugins)
+        plugins = sorted(plugins, key=lambda p: p.priority, reverse=True)
+        for plugin in plugins:
             callbacks = plugin.callbacks
             if etype not in callbacks:
                 continue

edmond/plugin.py

@@ -9,6 +9,7 @@ class Plugin:
     def __init__(self, bot):
         self.bot = bot
         self.name = self.__class__.__name__.lower()[:-6]  # Remove "Plugin".
+        self.priority = 0
         self.config = self.__get_config()
         self.is_ready = self.__check_config()