[YouTube] Pass nsig value as return hook, fixes player `3bb1f723`

test/test_youtube_signature.py

@@ -1,4 +1,5 @@
 #!/usr/bin/env python
+# coding: utf-8
 
 from __future__ import unicode_literals
 
@@ -275,7 +276,8 @@ def signature(jscode, sig_input):
 
 def n_sig(jscode, sig_input):
     funcname = YoutubeIE(FakeYDL())._extract_n_function_name(jscode)
-    return JSInterpreter(jscode).call_function(funcname, sig_input)
+    return JSInterpreter(jscode).call_function(
+        funcname, sig_input, _ytdl_do_not_return=sig_input)
 
 
 make_sig_test = t_factory(

youtube_dl/extractor/youtube.py

@@ -1740,7 +1740,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
 
         def extract_nsig(s):
             try:
-                ret = func([s])
+                ret = func([s], kwargs={'_ytdl_do_not_return': s})
             except JSInterpreter.Exception:
                 raise
             except Exception as e: