add_url überschreiben

views.py

@login_required
def add_url(request):
    url = request.POST['url']
    if url == '':
        raise ValidationError("url must not be empty")
    if url.find("youtube"):
		test_str = subprocess.check_output("youtube-dl","-g", url)
		if test_str.find("http://"):
			UserSong(owner=request.user, url=test_str).save()
		else 
			raise ValidationError("can't get youtube url")
    else 
		UserSong(owner=request.user, url=url).save()
    return HttpResponseRedirect(reverse('cannen.views.index'))