[V3 Downloader] Add install messages from info.json (#1453)

redbot/cogs/downloader/downloader.py

@@ -220,7 +220,7 @@ async def _repo_add(self, ctx, name: str, repo_url: str, branch: str=None):
         """
         try:
             # noinspection PyTypeChecker
-            await self._repo_manager.add_repo(
+            repo = await self._repo_manager.add_repo(
                 name=name,
                 url=repo_url,
                 branch=branch
@@ -232,6 +232,8 @@ async def _repo_add(self, ctx, name: str, repo_url: str, branch: str=None):
             log.exception(_("Something went wrong during the cloning process."))
         else:
             await ctx.send(_("Repo `{}` successfully added.").format(name))
+            if repo.install_msg is not None:
+                await ctx.send(repo.install_msg)
 
     @repo.command(name="delete")
     async def _repo_del(self, ctx, repo_name: Repo):
@@ -268,7 +270,7 @@ async def _cog_install(self, ctx, repo_name: Repo, cog_name: str):
         """
         Installs a cog from the given repo.
         """
-        cog = discord.utils.get(repo_name.available_cogs, name=cog_name)
+        cog = discord.utils.get(repo_name.available_cogs, name=cog_name)  # type: Installable
         if cog is None:
             await ctx.send(_("Error, there is no cog by the name of"
                            " `{}` in the `{}` repo.").format(cog_name, repo_name.name))
@@ -286,6 +288,8 @@ async def _cog_install(self, ctx, repo_name: Repo, cog_name: str):
         await repo_name.install_libraries(self.SHAREDLIB_PATH)
 
         await ctx.send(_("`{}` cog successfully installed.").format(cog_name))
+        if cog.install_msg is not None:
+            await ctx.send(cog.install_msg)
 
     @cog.command(name="uninstall")
     async def _cog_uninstall(self, ctx, cog_name: InstalledCog):