Description of problem:

`dnf playground` with any of its subcommands (enable, disable and upgrade) throws an error and fails.


Version-Release number of selected component (if applicable):

4.0.19


How reproducible:

Always


Steps to Reproduce:

1. Open terminal
2. Run `dnf playground enable` or `dnf playground disable` or `dnf playground upgrade`


Actual results:

Python throws an error


Expected results:

DNF enables, disables or upgrades Playground repo


Additional info:

Thrown error:

Traceback (most recent call last):
  File "/usr/bin/dnf", line 58, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 201, in user_main
    errcode = main(args)
  File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 67, in main
    return _main(base, args, cli_class, option_parser_class)
  File "/usr/lib/python3.9/site-packages/dnf/cli/main.py", line 102, in _main
    cli.configure(list(map(ucd, args)), option_parser())
  File "/usr/lib/python3.9/site-packages/dnf/cli/cli.py", line 881, in configure
    self.command.configure()
  File "/usr/lib/python3.9/site-packages/dnf-plugins/copr.py", line 144, in configure
    if len(self.opts.arg):
AttributeError: 'Namespace' object has no attribute 'arg'