[hls] Better FairPlay DRM detection (#1661)

Authored by: nyuszika7h

yt_dlp/downloader/hls.py

@@ -77,6 +77,15 @@ class HlsFD(FragmentFD):
                 message = ('The stream has AES-128 encryption and neither ffmpeg nor pycryptodomex are available; '
                            'Decryption will be performed natively, but will be extremely slow')
         if not can_download:
+            has_drm = re.search('|'.join([
+                r'#EXT-X-FAXS-CM:',  # Adobe Flash Access
+                r'#EXT-X-(?:SESSION-)?KEY:.*?URI="skd://',  # Apple FairPlay
+            ]), s)
+            if has_drm and not self.params.get('allow_unplayable_formats'):
+                self.report_error(
+                    'This video is DRM protected; Try selecting another format with --format or '
+                    'add --check-formats to automatically fallback to the next best format')
+                return False
             message = message or 'Unsupported features have been detected'
             fd = FFmpegFD(self.ydl, self.params)
             self.report_warning(f'{message}; extraction will be delegated to {fd.get_basename()}')