fix: KID extraction error handling

+ extract_kid method will raise an error if the file does not exist
+ If KID extraction fails, the lecture will be skipped instead of causing the program to exit

main.py

@@ -918,11 +918,19 @@ def handle_segments(url, format_id, video_title,
         print("Return code from the downloader was non-0 (error), skipping!")
         return
 
-    video_kid = extract_kid(video_filepath_enc)
-    print("KID for video file is: " + video_kid)
+    try:
+        video_kid = extract_kid(video_filepath_enc)
+        print("KID for video file is: " + video_kid)
+    except Exception as e:
+        print(f"Error extracting video kid: {e}")
+        return
 
-    audio_kid = extract_kid(audio_filepath_enc)
-    print("KID for audio file is: " + audio_kid)
+    try:
+        audio_kid = extract_kid(audio_filepath_enc)
+        print("KID for audio file is: " + audio_kid)
+    except Exception as e:
+        print(f"Error extracting audio kid: {e}")
+        return
 
     try:
         decrypt(video_kid, video_filepath_enc, video_filepath_dec)

utils.py

@@ -2,6 +2,7 @@ import mp4parse
 import codecs
 import widevine_pssh_pb2
 import base64
+import os
 
 def extract_kid(mp4_file):
     """
@@ -18,6 +19,8 @@ def extract_kid(mp4_file):
     """
 
     boxes = mp4parse.F4VParser.parse(filename=mp4_file)
+    if not os.path.exists(mp4_file):
+        raise Exception("File does not exist")
     for box in boxes:
         if box.header.box_type == 'moov':
             pssh_box = next(x for x in box.pssh if x.system_id == "edef8ba979d64acea3c827dcd51d21ed")