[vgtv] Fix tests' exts
[tvigle] Replace 404 test
[tvigle] Extract format file sizes
[core] Decode environment variables with filesystem encoding (Fixes #3854, Fixes #3217, Fixes #2918)

Introduces compat versions of os.getenv and os.path.expanduser
[nfl] Use compatible urlparse
[generic] Delete test case

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[utils] Fix js_to_json
[utils] Improve and test js_to_json
[utils] Add posix expanduser implementation and clarify the original source
[sunporno] Fix duration extraction and make more robust
[spankwire] Fix extraction
[tapely] Add new extractor (closes #3861)
[izlesene] Prepend scheme to thumbnails
[tapely] Catch SoundCloud tracks
[jpopsuki] Support category links
[walla] Add new extractor
[dropbox] Fix the video url query (fixes #3868)

Previously it would convert urls without a query into 'something.mp4&dl=1'
Merge pull request #3865 from diffycat/jpopsuki

[jpopsuki] Support category links
[jpopsukitv] Improve _VALID_URL and modernize
[jpopsuki] More modernize