code: def on_nick(self, connection, event):
          
          old_nickname = self.get_nickname(event)
          old_color = self.nicknames.pop(old_nickname)
          new_nickname = event.target()
          message = "is now known as %s" % new_nickname
          self.namespace.emit("message", old_nickname, message, old_color)
          new_color = color(new_nickname)
          self.nicknames[new_nickname] = new_color
          self.emit_nicknames()
          if self.nickname == old_nickname:
              self.nickname = new_nickname
docs: Someone changed their nickname - send the nicknames list to the
          WebSocket.