Tenía el siguiente problema usando fedora 22
# dnf update
Traceback (most recent call last):
File "/bin/dnf", line 36, in
main.user_main(sys.argv[1:], exit_code=True)
File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 198, 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 117, in _main
cli.configure(map(ucd, args))
File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 1007, in configure
self.optparser.usage = self.optparser.get_usage()
File "/usr/lib/python2.7/site-packages/dnf/cli/option_parser.py", line 273, in get_usage
usage += "%-25s %s\n" % (name, summary)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 40: ordinal not in range(128)
La solución a este problema, se encuentra en ésta página:
Solo es necesario ejecutar como root:
env LANG=C sudo dnf clean all && env LANG=C sudo dnf -y update