Update Translation documentation
raise ItemNotFoundError if course not found in modulestore (course_listing)
STUD-1455
Add acceptance test for blocked YouTueb API with HTML5 sources

When the video has both YouTube IDs and HTML5 sources, and
the YouTube API is blocked, then HTML5 sources should be
used.
Addressing comments.
Merge pull request #3010 from edx/zub/bugfix/std1455-studioaccessissue

raise ItemNotFoundError if course not found in modulestore (course_listing)
Merge pull request #3102 from edx/valera/add_acceptance_test_youtube_html5_blocked_api

Add acceptance test for blocked YouTueb API with HTML5 sources
Merge pull request #3115 from edx/sarina/update-i18n-translators-docs

Update Translation documentation
BLD-950: Update captions logic on front-end.