dnf in Fedora 27 is throwing a python error

Question

I am looking to upgrade from Fedora 27 however, DNF has broken somehow.

$ dnf upgrade
Traceback (most recent call last):
  File "/bin/dnf", line 58, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 179, in user_main
    errcode = main(args)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 64, in main
    return _main(base, args, cli_class, option_parser_class)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 99, in _main
    return cli_run(cli, base)
  File "/usr/lib/python3.6/site-packages/dnf/cli/main.py", line 115, in cli_run
    cli.run()
  File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 1013, in run
    self._process_demands()
  File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 766, in _process_demands
    load_available_repos=self.demands.available_repos)
  File "/usr/lib/python3.6/site-packages/dnf/base.py", line 353, in fill_sack
    self._add_repo_to_sack(r)
  File "/usr/lib/python3.6/site-packages/dnf/base.py", line 122, in _add_repo_to_sack
    hrepo.filelists_fn = repo._filelists_fn
TypeError: Expected a string or a unicode object

Here are the versions of the packages I have installed:

$ rpm -q dnf python3-dnf python3 python3-rpm
dnf-2.7.5-2.fc27.noarch
python3-dnf-2.7.5-2.fc27.noarch
python3-3.6.6-1.fc27.x86_64
python3-rpm-4.14.2.1-1.fc27.x86_64

I have tried re-installing the dnf package from koji (https://koji.fedoraproject.org/koji/buildinfo?buildID=1006088), but it didn't make a difference. I am not sure what else I can try. I haven't used dnf in a while since it became EOL but now I would like to upgrade, and it has surprised me with this error. Is it possible to track down what has occurred so I can fix dnf and eventually upgrade?

Answer 1

So I asked this question on the Fedora Project forum, see the full conversation here: https://ask.fedoraproject.org/t/fedora-27-dnf-throwing-python-error-cannot-upgrade/1463

tl;dr - I had to disable a PlexRepo then run dnf clean all then dnf upgrade --refresh. Doing those commands without disabling the PlexRepo would throw the error, so there must have been a problem with that repository.