[itv] fixed extraction (closes ytdl-org#28906)

https://github.com/ytdl-org/youtube-dl/pull/28955 (@sleaux-meaux)
ITV changes require media stream and subtitles to be taken
from different playlist resources. Incorporates suggestion in
ytdl-org#28906 (comment)

youtube_dl/extractor/itv.py

@@ -15,6 +15,7 @@ from ..utils import (
     merge_dicts,
     parse_duration,
     smuggle_url,
+    try_get,
     url_or_none,
 )
 
@@ -23,15 +24,20 @@ class ITVIE(InfoExtractor):
     _VALID_URL = r'https?://(?:www\.)?itv\.com/hub/[^/]+/(?P<id>[0-9a-zA-Z]+)'
     _GEO_COUNTRIES = ['GB']
     _TESTS = [{
-        'url': 'https://www.itv.com/hub/liar/2a4547a0012',
+        'url': 'https://www.itv.com/hub/the-durrells/2a4156a0001',
         'info_dict': {
-            'id': '2a4547a0012',
+            'id': '2a4156a0001',
             'ext': 'mp4',
-            'title': 'Liar - Series 2 - Episode 6',
-            'description': 'md5:d0f91536569dec79ea184f0a44cca089',
-            'series': 'Liar',
-            'season_number': 2,
-            'episode_number': 6,
+            'title': 'The Durrells - Series 1 - Episode 1',
+            'description': 'md5:43ae58e27aa91720fc933a68a37e9e95',
+            'series': 'The Durrells',
+            'season_number': 1,
+            'episode_number': 1,
+            'subtitles': {
+                'en': [
+                    {'url': 'https://itvpnpsubtitles.content.itv.com/2-4156-0001-003/Subtitles/3/WebVTT-OUT-OF-BAND/2-4156-0001-003_Series1590486890_TX000000.vtt'}
+                ]
+            },
         },
         'params': {
             # m3u8 download
@@ -87,13 +93,13 @@ class ITVIE(InfoExtractor):
                 },
                 'variantAvailability': {
                     'featureset': {
-                        'min': ['hls', 'aes', 'outband-webvtt'],
-                        'max': ['hls', 'aes', 'outband-webvtt']
+                        'min': ['hls', 'aes'],
+                        'max': ['hls', 'aes']
                     },
-                    'platformTag': 'dotcom'
+                    'platformTag': 'mobile'
                 }
             }).encode(), headers=headers)
-        video_data = ios_playlist['Playlist']['Video']
+        video_data = try_get(ios_playlist, lambda x: x['Playlist']['Video'], dict) or {}
         ios_base_url = video_data.get('Base')
 
         formats = []
@@ -114,8 +120,36 @@ class ITVIE(InfoExtractor):
                 })
         self._sort_formats(formats)
 
+        subs_playlist = self._download_json(
+            ios_playlist_url, video_id, data=json.dumps({
+                'user': {
+                    'itvUserId': '',
+                    'entitlements': [],
+                    'token': ''
+                },
+                'device': {
+                    'manufacturer': 'Safari',
+                    'model': '5',
+                    'os': {
+                        'name': 'Windows NT',
+                        'version': '6.1',
+                        'type': 'desktop'
+                    }
+                },
+                'client': {
+                    'version': '4.1',
+                    'id': 'browser'
+                },
+                'variantAvailability': {
+                    'featureset': {
+                        'min': ['mpeg-dash', 'widevine', 'outband-webvtt'],
+                        'max': ['mpeg-dash', 'widevine', 'outband-webvtt']
+                    },
+                    'platformTag': 'mobile'
+                }
+            }).encode(), headers=headers)
+        subs = try_get(subs_playlist, lambda x: x['Playlist']['Video']['Subtitles'], list) or []
         subtitles = {}
-        subs = video_data.get('Subtitles') or []
         for sub in subs:
             if not isinstance(sub, dict):
                 continue