Added test case for original video downloading, Updated md5 and
duration for the old test case as google probably changed how video
processing works on their servers, breaking the md5 and duration tests.
Recently eporner slightly changed the URL layout, the ID that used to be
digits only are now digits and letters, so youtube-dl falls back to
the generic extractor that doesn't work.
Fix the matching regex to allow letters in ID.
[v2: added a test case]
* [bandcamp] raise ExtractorError when track not streamable
* [bandcamp] update md5 for second test
* don't rely on json-data, but just check for 'file'
* don't rely on presence of 'file'