Description of problem:
* install dnf3 tracer plugin
* update pacake with dnf-3

Version-Release number of selected component:
python3-dnf-0.6.3-2.fc21

Additional info:
reporter:       libreport-2.3.0
executable:     /bin/dnf-3
kernel:         3.18.6-200.fc21.x86_64
runlevel:       N 5
type:           Python3
uid:            0

Truncated backtrace:
tracer.py:93:_print_output:TypeError: Type str doesn't support the buffer API

Traceback (most recent call last):
  File "/bin/dnf-3", 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 182, 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 141, in _main
    ret = resolving(cli, base)
  File "/usr/lib/python3.4/site-packages/dnf/cli/main.py", line 160, in resolving
    base.do_transaction()
  File "/usr/lib/python3.4/site-packages/dnf/cli/cli.py", line 221, in do_transaction
    self.plugins.run_transaction()
  File "/usr/lib/python3.4/site-packages/dnf/plugin.py", line 82, in fn
    dnf.util.mapall(operator.methodcaller(method), self.plugins)
  File "/usr/lib/python3.4/site-packages/dnf/util.py", line 157, in mapall
    return list(map(fn, *seq))
  File "/usr/lib/python3.4/site-packages/dnf-plugins/tracer.py", line 67, in transaction
  File "/usr/lib/python3.4/site-packages/dnf-plugins/tracer.py", line 93, in _print_output
TypeError: Type str doesn't support the buffer API

Local variables in innermost frame:
out: b'You should restart:\n  * These applications manually:\n      abrt-applet\n      firefox\n      nm-applet\n      polkit-gnome-authentication-agent-1\n      seapplet\n      ssh-agent\n      tracker-extract\n      tracker-miner-apps\n      tracker-miner-user-guides\n      tracker-store\n      virt-manager\n      xfdesktop\n      xscreensaver\n\nAdditionally to those process above, there are:\n  - 1 processes requiring restart of your session (i.e. Logging out & Logging in again)\n'