Follow-up of #5892
This marks all url attributes in the validation schema as optional. Probably only necessary for HLS and DASH stream URLs, but I added it to progressive HTTP streams and subtitle URLs as well. Doesn't hurt...
master
$ streamlink https://vimeo.com/event/4154130/embed
[cli][info] Found matching plugin vimeo for URL https://vimeo.com/event/4154130/embed
error: Unable to validate result: ValidationError(dict):
Unable to validate value of key 'request'
Context(dict):
Unable to validate value of key 'files'
Context(dict):
Unable to validate value of key 'hls'
Context(dict):
Unable to validate value of key 'cdns'
Context(dict):
Unable to validate value
Context(dict):
Key 'url' not found in {'origin': 'studio'}
PR
$ streamlink https://vimeo.com/event/4154130/embed
[cli][info] Found matching plugin vimeo for URL https://vimeo.com/event/4154130/embed
error: No playable streams found on this URL: https://vimeo.com/event/4154130/embed