523ebc9b0b
Simplified universal serialization support in json.dump() can be achieved by passing 'default=str', which was already the case in DataJob.run() for -j/--dump-json, but not for the 'metadata' post-processor. This commit introduces util.dump_json() that (more or less) unifies the JSON output procedure of both --write-metadata and --dump-json. (#251, #252)