code: def extract_classifier_and_extension(pkg_name, filename):
      
      basename, _, extension = filename.rpartition('.')
      if extension == 'gz' and filename.endswith('.tar.gz'):
          extension = 'tar.gz'
          basename = filename[:-7]
      if basename == pkg_name or basename[len(pkg_name)] != '-':
          return 'py2.py3-none-any', extension
      basename = basename[len(pkg_name)+1:]
      classifier_parts = basename.split('-')
      if len(classifier_parts) < 3:
          return 'py2.py3-none-any', extension
      if len(classifier_parts) == 3:
          _, _, classifier_parts[0] = classifier_parts[0].rpartition('.')
      return '-'.join(classifier_parts[-3:]), extension
docs: Returns a PEP425-compliant classifier (or 'py2.py3-none-any' if it cannot be extracted),
      and the file extension
      TODO: return a classifier 3-members namedtuple instead of a single string