# Buggy code
async def _perms_whitelist_add(self, ctx: commands.Context, *, keyword: str):
    """Adds a keyword to the whitelist.

    If anything is added to whitelist, it will blacklist everything else.
    """
    keyword = keyword.lower().strip()
    if not keyword:
        return await ctx.send_help()
    exists = False
    async with self.config.guild(ctx.guild).url_keyword_whitelist() as whitelist:
        if keyword in whitelist:
            exists = True
        else:
            whitelist.append(keyword)
    if exists:
        return await self._embed_msg(ctx, _("Keyword already in the whitelist."))
    else:
        embed = discord.Embed(
            title=_("Whitelist modified"), colour=await ctx.embed_colour()
        )
        embed.description = _("Added: `{whitelisted}` to the whitelist.").format(
            whitelisted=keyword
        )
        await ctx.send(embed=embed)


# Traceback (RuntimeError)
Traceback (most recent call last):
File "/home/martinebots/martinebotsvenv/lib/python3.7/site-packages/discord/ext/commands/core.py", line 79, in wrapped
ret = await coro(*args, **kwargs)
File "/home/martinebots/martinebotscogs/cogs_modified/audio/audio.py", line 3183, in play
await self._enqueue_tracks(ctx, query)
File "/home/martinebots/martinebotscogs/cogs_modified/audio/audio.py", line 3885, in _enqueue_tracks
result, called_api = await self.music_cache.lavalink_query(ctx, player, query)
File "/home/martinebots/martinebotscogs/cogs_modified/audio/apis.py", line 911, in lavalink_query
results = await player.load_tracks(query)
File "/home/martinebots/martinebotsvenv/lib/python3.7/site-packages/lavalink/rest_api.py", line 300, in load_tracks
self.__check_node_ready()
File "/home/martinebots/martinebotsvenv/lib/python3.7/site-packages/lavalink/rest_api.py", line 268, in __check_node_ready
raise RuntimeError("Cannot execute REST request when node not ready.")
RuntimeError: Cannot execute REST request when node not ready.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/home/martinebots/martinebotsvenv/lib/python3.7/site-packages/discord/ext/commands/bot.py", line 863, in invoke
await ctx.command.invoke(ctx)
File "/home/martinebots/martinebotsvenv/lib/python3.7/site-packages/discord/ext/commands/core.py", line 728, in invoke
await injected(*ctx.args, **ctx.kwargs)
File "/home/martinebots/martinebotsvenv/lib/python3.7/site-packages/discord/ext/commands/core.py", line 88, in wrapped
raise CommandInvokeError(exc) from exc
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: RuntimeError: Cannot execute REST request when node not ready.```

# Fixed code
async def _perms_whitelist_add(self, ctx: commands.Context, *, keyword: str):
    """Adds a keyword to the whitelist.

    If anything is added to whitelist, it will blacklist everything else.
    """
    keyword = keyword.lower().strip()
    if not keyword:
        return await ctx.send_help()
    exists = False
    async with self.config.guild(ctx.guild).url_keyword_whitelist() as whitelist:
        if keyword in whitelist:
            exists = True
        else:
            whitelist.append(keyword)
    if exists:
        return await self._embed_msg(ctx, title=_("Keyword already in the whitelist."))
    else:
        return await self._embed_msg(
            ctx,
            title=_("Whitelist Modified"),
            description=_("Added: `{whitelisted}` to the whitelist.").format(
                whitelisted=keyword
            ),
        )