Channel: use general pbj=1 endpoint to get first page of videos

YouTube disabled the browse_ajax endpoint. Quick fix for first
channel page. In general, this will be more robust against api
endpoint changes. As YouTube continues to change api endpoints,
at least the subscriptions and first page will no longer break.

youtube/channel.py

@@ -186,7 +186,11 @@ def post_process_channel_info(info):
         util.add_extra_html_info(item)
 
 
-
+def get_channel_first_page(base_url=None, channel_id=None):
+    if channel_id:
+        base_url = 'https://www.youtube.com/channel/' + channel_id
+    return util.fetch_url(base_url + '/videos?pbj=1&view=0', headers_desktop,
+                          debug_name='gen_channel_videos')
 
 
 playlist_sort_codes = {'2': "da", '3': "dd", '4': "lad"}
@@ -203,7 +207,7 @@ def get_channel_page_general_url(base_url, tab, request, channel_id=None):
     query = request.args.get('query', '')
     ctoken = request.args.get('ctoken', '')
 
-    if tab == 'videos' and channel_id:
+    if tab == 'videos' and channel_id and page_number > 1:
         tasks = (
             gevent.spawn(get_number_of_videos_channel, channel_id),
             gevent.spawn(get_channel_tab, channel_id, page_number, sort,
@@ -213,9 +217,13 @@ def get_channel_page_general_url(base_url, tab, request, channel_id=None):
         util.check_gevent_exceptions(*tasks)
         number_of_videos, polymer_json = tasks[0].value, tasks[1].value
     elif tab == 'videos':
+        if channel_id:
+            num_videos_call = (get_number_of_videos_channel, channel_id)
+        else:
+            num_videos_call = (get_number_of_videos_general, base_url)
         tasks = (
-            gevent.spawn(get_number_of_videos_general, base_url),
-            gevent.spawn(util.fetch_url, base_url + '/videos?pbj=1&view=0', headers_desktop, debug_name='gen_channel_videos')
+            gevent.spawn(*num_videos_call),
+            gevent.spawn(get_channel_first_page, base_url=base_url),
         )
         gevent.joinall(tasks)
         util.check_gevent_exceptions(*tasks)

youtube/subscriptions.py

@@ -457,7 +457,7 @@ def _get_upstream_videos(channel_id):
 
     tasks = (
         # channel page, need for video duration
-        gevent.spawn(_get_channel_tab, channel_id, channel_status_name),
+        gevent.spawn(channel.get_channel_first_page, channel_id=channel_id),
         # need atoma feed for exact published time
         gevent.spawn(_get_atoma_feed, channel_id)
     )