better JS fetching

pytube/__main__.py

@@ -131,17 +131,13 @@ class YouTube:
                 apply_descrambler(self.vid_info, fmt)
             apply_descrambler(self.player_config_args, fmt)
 
-            try:
-                apply_signature(
-                    self.player_config_args, fmt, self.js  # type: ignore
-                )
-            except TypeError:
+            if not self.js:
                 if not self.embed_html:
                     self.embed_html = request.get(url=self.embed_url)
                 self.js_url = extract.js_url(self.embed_html)
                 self.js = request.get(self.js_url)
-                assert self.js is not None
-                apply_signature(self.player_config_args, fmt, self.js)
+
+            apply_signature(self.player_config_args, fmt, self.js)
 
             # build instances of :class:`Stream <Stream>`
             self.initialize_stream_objects(fmt)

pytube/extract.py

@@ -242,12 +242,7 @@ def apply_signature(config_args: Dict, fmt: str, js: str) -> None:
             logger.debug("signature found, skip decipher")
             continue
 
-        if js is not None:
-            signature = cipher.get_signature(ciphered_signature=stream["s"])
-        else:
-            # signature not present in url (line 33), need js to descramble
-            # TypeError caught in __main__
-            raise TypeError("JS is None")
+        signature = cipher.get_signature(ciphered_signature=stream["s"])
 
         logger.debug("finished descrambling signature for itag=%s", stream["itag"])
         # 403 forbidden fix