title: Getting KeyError: 'url' with PyTube
body: <p>I get the error sometimes when downloading a video. For example, I can attempt to download the video and it will download, the next time I run the script that video will not download and the error will be thrown.</p>
  
  <pre><code>def search_youtube(song,randomString,playlist_name):
   results = YoutubeSearch(song, max_results=1).to_dict()
   for v in results:
      url = 'https://www.youtube.com' + v['link']
      print(url)
  
      _filename = song
      format_input = 'mp4'
      format_output = 'mp3'
  
      print("Downloading...." + ' ' + song)
      time.sleep(5)
      YouTube(url).streams.first().download(filename=randomString,output_path=playlist_name)
  </code></pre>