Description of problem:
"dnf repoquery --disablerepo=\* --enablerepo=fedora-source --arch=src --whatrequires db4-devel"

Version-Release number of selected component:
dnf-2.6.2-1.fc26

Additional info:
reporter:       libreport-2.9.1
cmdline:        /usr/libexec/system-python /usr/bin/dnf repoquery --disablerepo=* --enablerepo=fedora-source --arch=src --whatrequires db4-devel
crash_function: arch
exception_type: AssertionError
executable:     /usr/bin/dnf
kernel:         4.11.9-300.fc26.x86_64
runlevel:       N 5
type:           Python3
uid:            1001

Truncated backtrace:
config.py:908:arch:AssertionError

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/python3.6/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 95, in _main
    cli.configure(list(map(ucd, args)), option_parser())
  File "/usr/lib/python3.6/site-packages/dnf/cli/cli.py", line 909, in configure
    self.base.conf._configure_from_options(opts)
  File "/usr/lib/python3.6/site-packages/dnf/conf/config.py", line 843, in _configure_from_options
    setattr(self, name, value)
  File "/usr/lib/python3.6/site-packages/dnf/conf/config.py", line 908, in arch
    assert(val in dnf.rpm._BASEARCH_MAP.keys())
AssertionError

Local variables in innermost frame:
val: 'src'
self: <dnf.conf.config.MainConf object at 0x7fbb67991630>