Accommodate newer Sphinx versions that use pathlib

sphinx_automodapi/automodsumm.py

@@ -663,7 +663,7 @@ def get_members_class(obj, typ, include_public=[],
  # An important subtlety here is that the path we pass in has
  # to be relative to the file being generated, so we have to
  # figure out the right number of '..'s
- ndirsback = path.replace(base_path, '').count(os.sep)
+ ndirsback = path.replace(str(base_path), '').count(os.sep)
  ref_file_rel_segments = ['..'] * ndirsback
  ref_file_rel_segments.append(mod_name_dir)
  ref_file_rel_segments.append('references.txt')