docs: def _validate_bagittxt(self):
          """
          Verify that bagit.txt conforms to specification
          """
          bagit_file_path = os.path.join(self.path, "bagit.txt")
          with open(bagit_file_path, 'r') as bagit_file:
              first_line = bagit_file.readline()
              if first_line.startswith(BOM):
                  raise BagValidationError("bagit.txt must not contain a byte-order mark")