title: Change the permissions of a discord text channel with discord.py
body: <p>I would have liked to make a command that allows to modify the permissions of a particular text channel discord with discord.py. For example, disable sending messages in a specific channel.</p>
  
  <p>I looked at the documentation of discord.py and I saw that there is a PermissionOverwrite class (<a href="https://discordpy.readthedocs.io/en/latest/api.html?highlight=app#permissionoverwrite" rel="nofollow noreferrer">https://discordpy.readthedocs.io/en/latest/api.html?highlight=app#permissionoverwrite</a>) allowing to do some things at the level of the permissions (notably with the function update)</p>
  
  <pre class="lang-py prettyprint-override"><code>@client.command()
  async def perm(ctx):
          perms = discord.Permissions()
          ctx.channel.perms.update(send_messages=False)
  </code></pre>
  
  <p>Command raised an exception: AttributeError: 'TextChannel' object has no attribute 'perms'</p>