Pysox is currently broken due to a breaking change from setuptools as described here: pypa/setuptools#4870

setuptools.errors.InvalidConfigError: Invalid dash-separated key 'description-file' in 'metadata' (setup.cfg), please use the underscore name        
      'description_file' instead.

The fix is easy enough. As the error suggests just change description-file to description_file in your setup.cfg