code: def get_local_file_list(self):
          
          file_list = []
          for (dirpath, dirnames, filenames) in os.walk(self.build_dir):
              for fname in filenames:
                  # relative path, to sync with the S3 key
                  local_key = os.path.join(
                      os.path.relpath(dirpath, self.build_dir),
                      fname
                  )
                  if local_key.startswith('./'):
                      local_key = local_key[2:]
                  file_list.append(local_key)
          return file_list
docs: Walk the local build directory and create a list of relative and
          absolute paths to files.