[extractor/TwitCasting] fix: Use UserNotLive

[at-wat]

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Description of your pull request and other information

Running yt-dlp with --wait-for-video option for TwitCastingLive URL results an error:

$ yt-dlp --wait-for-video=30 https://twitcasting.tv/channel_name
[TwitCastingLive] Extracting URL: https://twitcasting.tv/channel_name
[TwitCastingLive] Downloading live video of user channel_name. Pass "https://twitcasting.tv/channel_name/show" to download the history
[TwitCastingLive] channel_name: Downloading webpage
[TwitCastingLive] channel_name: Downloading live history
ERROR: [TwitCastingLive] channel_name: The user is not currently live; please report this issue on  https://github.com/yt-dlp/yt-dlp/issues?q= , filling out the appropriate issue template. Confirm you are on the latest version using  yt-dlp -U
$

This is caused since class TwitCastingLiveIE raises ExtractorError instead of UserNotLive when the channel is currently not live.

This PR fixes TwitCastingIE to raise UserNotLive when the channel isn't live.
--wait-for-video option for TwitCasting works with this branch as below:

$ yt-dlp --wait-for-video=30 https://twitcasting.tv/channel_name
[TwitCastingLive] Extracting URL: https://twitcasting.tv/channel_name
[TwitCastingLive] Downloading live video of user channel_name. Pass "https://twitcasting.tv/channel_name/show" to download the history
[TwitCastingLive] channel_name: Downloading webpage
[TwitCastingLive] channel_name: Downloading live history
WARNING: [TwitCastingLive] channel_name: The channel is not currently live
[wait] Waiting for 00:00:30 - Press Ctrl+C to try now
[wait] Remaining time until next attempt: 00:00:22

Added a test case to check the raised exception against a dummy TwitCasting account which won't be live.

$ python test/test_download.py TestDownload.test_TwitCastingLive_all
[debug] Loaded 1864 extractors
[TwitCastingLive] Extracting URL: https://twitcasting.tv/c:unusedlive
[TwitCastingLive] Downloading live video of user c:unusedlive. Pass "https://twitcasting.tv/c:unusedlive/show" to download the history
[TwitCastingLive] c:unusedlive: Downloading webpage
[TwitCastingLive] c:unusedlive: Downloading live history
ERROR: [TwitCastingLive] c:unusedlive: The channel is not currently live
  File "/home/at-wat/Downloads/yt-dlp/yt_dlp/extractor/common.py", line 715, in extract
    ie_result = self._real_extract(url)
                ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/at-wat/Downloads/yt-dlp/yt_dlp/extractor/twitcasting.py", line 267, in _real_extract
    raise UserNotLive(video_id=uploader_id)

.
----------------------------------------------------------------------
Ran 1 test in 0.487s

OK
$ 

Template

Before submitting a pull request make sure you have:

• At least skimmed through contributing guidelines including yt-dlp coding conventions
• Searched the bugtracker for similar pull requests
• Checked the code with flake8 and ran relevant tests

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What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)
• New extractor (Piracy websites will not be accepted)
• Core bug fix/improvement
• New feature (It is strongly recommended to open an issue first)

Copilot Summary

🤖 Generated by Copilot at 48e7bb8

Summary

🧪🚨🎥

This pull request enhances the testing and error handling of test_download and twitcasting modules. It adds support for testing expected exceptions in test_download and raises a specific exception for non-live streams in twitcasting.

YoutubeDLError is the sign of doom
We skip the tests that seal our fate
UserNotLive is the curse we loom
We raise the exception and test our hate

Walkthrough

• Import YoutubeDLError and UserNotLive exceptions from yt_dlp.utils (link, link)
• Add and modify test cases for TwitCastingLiveIE extractor to expect UserNotLive exception when user is not live (link, link)
• Raise UserNotLive exception in TwitCastingLiveIE._real_extract method when current_live value is missing from webpage (link)
• Add helper method to check if raised exception matches expected exception in test function (link)
• Call helper method in except blocks and return or re-raise exception accordingly in test function (link, link)

[pukkandan]

LGTM. But the core and extractor changes should be merged in separate commits