[V3 Admin] Rewrite of Squid-Plugins Admin cog (#825)

* Add/remove roles

* Announcement

* Edit role stuff

A bit of refactoring

* Selfrole stuff

* Add announce ignore capabilities

* announce configurations

Announcement fixes

* Serverlock initial commit

* Add some admin tests

better test

* Update for new config

* Add user hierarchy checks

* Fix tests

* Update from rebase

* Fix config getter

* Fix async getters/selfrole

redbot/cogs/admin/announcer.py

@@ -0,0 +1,71 @@
+import asyncio
+
+import discord
+from discord.ext import commands
+
+
+class Announcer:
+    def __init__(self, ctx: commands.Context,
+                 message: str,
+                 config=None):
+        """
+        :param ctx:
+        :param message:
+        :param config: Used to determine channel overrides
+        """
+        self.ctx = ctx
+        self.message = message
+        self.config = config
+
+        self.active = None
+
+    def start(self):
+        """
+        Starts an announcement.
+        :return:
+        """
+        if self.active is None:
+            self.active = True
+            self.ctx.bot.loop.create_task(self.announcer())
+
+    def cancel(self):
+        """
+        Cancels a running announcement.
+        :return:
+        """
+        self.active = False
+
+    async def _get_announce_channel(self, guild: discord.Guild) -> discord.TextChannel:
+        channel_id = await self.config.guild(guild).announce_channel()
+        channel = None
+
+        if channel_id is not None:
+            channel = guild.get_channel(channel_id)
+
+        if channel is None:
+            channel = guild.default_channel
+
+        return channel
+
+    async def announcer(self):
+        guild_list = self.ctx.bot.guilds
+        bot_owner = (await self.ctx.bot.application_info()).owner
+        for g in guild_list:
+            if not self.active:
+                return
+
+            if await self.config.guild(g).announce_ignore():
+                continue
+
+            channel = await self._get_announce_channel(g)
+
+            try:
+                await channel.send(self.message)
+            except discord.Forbidden:
+                await bot_owner.send("I could not announce to guild: {}".format(
+                                         g.id
+                                     ))
+            await asyncio.sleep(0.5)
+
+        self.active = False
+