docs: def passphrase_file(passphrase=None):
      """Read passphrase from a file. This should only ever be
      used by our built in integration tests. At this time,
      during normal operation, only pinentry is supported for
      entry of passwords."""
      cmd = []
      pass_file = None
      if not passphrase and 'CRYPTORITO_PASSPHRASE_FILE' in os.environ:
          pass_file = os.environ['CRYPTORITO_PASSPHRASE_FILE']
          if not os.path.isfile(pass_file):
              raise CryptoritoError('CRYPTORITO_PASSPHRASE_FILE is invalid')
      elif passphrase:
          tmpdir = ensure_tmpdir()
          pass_file = "%s/p_pass" % tmpdir
          p_handle = open(pass_file, 'w')
          p_handle.write(passphrase)
          p_handle.close()
  
      if pass_file:
          cmd = cmd + ["--batch", "--passphrase-file", pass_file]
  
          vsn = gpg_version()
          if vsn[0] >= 2 and vsn[1] >= 1:
              cmd = cmd + ["--pinentry-mode", "loopback"]
  
      return cmd