title: Discord.py giveaway command random choice from reactions error
body: <p>I'm trying to make a giveaway command for my Discord.py bot. I used an guide from YouTube: <a href="https://youtu.be/s531M7jLh6A" rel="nofollow noreferrer">https://youtu.be/s531M7jLh6A</a> but it gets an error on <code>winner = random.choice(users) part:</code></p>
  <p>Full command:</p>
  <pre><code>@bot.command()
   @commands.has_permissions(manage_guild=True)
   async def gstart(ctx, mins : int, *, prize:str):
       embed=discord.Embed(color=0x0f84eb)
       embed.add_field(name=&quot;Giveaway!&quot;, value=f&quot;{prize}&quot;, inline=False)
       end = datetime.datetime.utcnow() + datetime.timedelta(seconds = mins*60)
       embed.add_field(name=&quot;Kończy się:&quot;, value= f&quot;{end} UTC&quot;)
       embed.set_footer(text=&quot;&lt;&gt; and hosted with ♡ by Maciejka&quot;)
       my_msg = await ctx.send(embed=embed)
       await my_msg.add_reaction('✋')
       await asyncio.sleep(10)
       new_msg = await ctx.channel.fetch_message(my_msg.id)
       users = new_msg.reactions[0].users().flatten()
       users.pop(users.index(bot.user))
       print('1')
       winner = random.choice(users)
       print('3')
       await ctx.send(f&quot;Congrats! {winner} won {prize}!&quot;)
  </code></pre>
  <p>Full error i got:</p>
  <pre><code>/usr/lib/python3.7/asyncio/events.py:88: RuntimeWarning: coroutine '_AsyncIterator.flatten' was never awaited
    self._context.run(self._callback, *self._args)
  RuntimeWarning: Enable tracemalloc to get the object allocation traceback
  </code></pre>