Traceback (most recent call last):
  File "/bin/dnf", line 36, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 182, in user_main
    errcode = main(args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 84, in main
    return _main(base, args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 141, in _main
    ret = resolving(cli, base)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 160, in resolving
    base.do_transaction()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 221, in do_transaction
    self.plugins.run_transaction()
  File "/usr/lib/python2.7/site-packages/dnf/plugin.py", line 82, in fn
    dnf.util.mapall(operator.methodcaller(method), self.plugins)
  File "/usr/lib/python2.7/site-packages/dnf/util.py", line 157, in mapall
    return list(map(fn, *seq))
  File "/usr/lib/python2.7/site-packages/dnf-plugins/tracer.py", line 59, in transaction
    args = ["tracer", "-n"] + list(installed | erased)
NameError: global name 'installed' is not defined