DNF fails with a traceback error "RuntimeError: invalid boolean value 'o'"

Issue

• Encountering DNF errors during package installation or update.
• Error message prevents successful use of DNF.

Traceback (most recent call last):
  File "/usr/lib64/python3.6/site-packages/libdnf/conf.py", line 2146, in ConfigParser__getboolean  
    return OptionBool(False).fromString(v)
  File "/usr/lib64/python3.6/site-packages/libdnf/conf.py", line 230, in fromString
    return _conf.OptionBool_fromString(self, value)
RuntimeError: invalid boolean value 'o'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/dnf", line 62, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 201, in user_main
    errcode = main(args)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 67, in main
    return _main(base, args, cli_class, option_parser_class)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 102, in _main
    cli.configure(list(map(ucd, args)), option_parser())
  File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 830, in configure
    self.base.init_plugins(opts.disableplugin, opts.enableplugin, self)
  File "/usr/lib/python3.6/site-packages/dnf/base.py", line 306, in init_plugins
    self._plugins._load(self.conf, disabled_glob, enable_plugins)
  File "/usr/lib/python3.6/site-packages/dnf/plugin.py", line 141, in _load
    self._check_enabled(conf, enable_plugins)
  File "/usr/lib/python3.6/site-packages/dnf/plugin.py", line 126, in _check_enabled
    and not parser.getboolean('main', 'enabled'))
  File "/usr/lib64/python3.6/site-packages/libdnf/conf.py", line 2148, in ConfigParser__getboolean
    raise ValueError('Not a boolean: %s' % v)
ValueError: Not a boolean: o