Discord.py sur heroku bot musique

music = {}
ytdl = youtube_dl.YoutubeDL()


class Video:
    def __init__(self, link):
        video = ytdl.extract_info(link, download=False)
        video_format = video["formats"][0]
        self.url = video["webpage_url"]
        self.stream_url = video_format["url"]
        self.title = video['title']
        self.duration = video['duration']
        self.thumbnail = video['thumbnail']
        return


def play_song(clients, queue, song):
    source = discord.PCMVolumeTransformer(discord.FFmpegPCMAudio(song.stream_url,
                                                                 before_options="-reconnect 1 -reconnect_streamed 1 -reconnect_delay_max 5"))

    def next(_):
        if len(queue) > 0:
            new_song = queue[0]
            del queue[0]
            play_song(clients, queue, new_song)
        else:
            asyncio.run_coroutine_threadsafe(clients.disconnect(), bot.loop)

    clients.play(source, after=next)

@bot.command()
async def play(ctx, url):
    if not ctx.message.author.voice:
        await ctx.send(" {} Vous devez vous connectez a un salon vocal !".format("<:no_entry:862022003639713892>"))
        return
    else:
        clients = ctx.guild.voice_client

        if clients and clients.channel:
            video = Video(url)
            music[ctx.guild].append(video)
        else:
            channels = ctx.message.author.voice.channel
            video = Video(url)
            music[ctx.guild] = []
            clients = await channels.connect()
            embed = discord.Embed(title="**Je met cette vidéo !**", color=0xFF0000, url=url)
            embed.set_author(name=ctx.author.name, icon_url=ctx.author.avatar_url)
            embed.set_thumbnail(url=video.thumbnail)
            embed.add_field(name="Titre :", value=video.title, inline=True)
            embed.add_field(name="Durée :", value=f"{video.duration}s", inline=True)
            await ctx.send(embed=embed)
            play_song(clients, music[ctx.guild], video)