k = end_line
    while k > start_line:
      backtrack_line = log_lines[k]
      build_failed = backtrack_line.startswith(FAILED_BUILD_LINE)
      if build_failed or not backtrack_line.startswith(BUILD_STATUS_LINE):
        tests_failed = False
      else:
        tests_failed = re.search(TESTS_FAILED_RE, backtrack_line)
      if build_failed or tests_failed:
        log_fragment = '\n'.join(