[root@oracle ax6]# dnf upgrade --refresh
MySQL 5.6 Community Server                                                                                                              2.0 MB/s | 354 kB     00:00
RPM Fusion for Fedora 21 - Free - Updates                                                                                               445 kB/s | 449 kB     00:01
RPM Fusion for Fedora 21 - Nonfree - Updates                                                                                            142 kB/s | 211 kB     00:01
RPM Fusion for Fedora 21 - Free                                                                                                         484 kB/s | 508 kB     00:01
mod_cloudflare Packages                                                                                                                  28 kB/s | 1.4 kB     00:00
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 185, 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 134, in _main
    cli.run()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 1058, in run
    self._process_demands()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 786, in _process_demands
    load_available_repos=lar)
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 237, in fill_sack
    self._add_repo_to_sack(r.id)
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 122, in _add_repo_to_sack
    load_updateinfo=True)
AssertionError: Can not load Yum repo.