Description of problem:
I want to build F23 image using command:

$ virt-builder fedora-23 --output fedora-23.qcow2 --format qcow2 --update

I got a stacktrace:
Traceback (most recent call last):
  File "/bin/dnf", line 35, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python3.4/site-packages/dnf/cli/main.py", line 198, in user_main
    errcode = main(args)
  File "/usr/lib/python3.4/site-packages/dnf/cli/main.py", line 84, in main
    return _main(base, args)
  File "/usr/lib/python3.4/site-packages/dnf/cli/main.py", line 144, in _main
    ret = resolving(cli, base)
  File "/usr/lib/python3.4/site-packages/dnf/cli/main.py", line 173, in resolving
    base.do_transaction(display=displays)
  File "/usr/lib/python3.4/site-packages/dnf/cli/cli.py", line 220, in do_transaction
    self.gpgsigcheck(downloadpkgs)
  File "/usr/lib/python3.4/site-packages/dnf/cli/cli.py", line 251, in gpgsigcheck
    if not sys.stdin.isatty() and not ay:
AttributeError: 'NoneType' object has no attribute 'isatty'

caused by 'dnf -y update' command.


Version-Release number of selected component (if applicable):
libguestfs-1.30.4-1.fc23.x86_64
libguestfs-tools-1.30.4-1.fc23.noarch