This port purports to convert json to yaml | yaml to json.
Attempting to convert a valid YAML file to JSON returns:

# json2yaml a-root.yml a-root.json
Traceback (most recent call last):
  File "/usr/local/bin/json2yaml", line 62, in <module>
    convert(json_file, yaml_file)
  File "/usr/local/bin/json2yaml", line 48, in convert
    loaded_json = json.load(json_file, object_pairs_hook=collections.OrderedDict)
  File "/usr/local/lib/python3.7/json/__init__.py", line 296, in load
    parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
  File "/usr/local/lib/python3.7/json/__init__.py", line 361, in loads
    return cls(**kw).decode(s)
  File "/usr/local/lib/python3.7/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/local/lib/python3.7/json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

As you can see I'm on python3.7. But the Makefile reports:
USES=		python:3.6+

The resultant .json file is 0 bytes in length.
Any help greatly appreciated.

Thanks.