||Returns the filname for the main test HTML file
||Validates the json specification for generating tests.
||Raised when the given combination of subresource type, source context type,
delivery type etc. are not supported and we should skip that configuration.
ShouldSkip is expected in normal generator execution (and thus subsequent
generation continues), as we first enumerate a broad range of configurations
first, and later raise ShouldSkip to filter out unsupported combinations.
ShouldSkip is distinguished from other general errors that cause immediate
termination of the generator and require fix.