Description of problem:
I just called command
  dnf history summary 764

According to dnf output this command should work
[root@host ~]# dnf history help
Invalid history sub-command, use: list, info, summary, redo, undo, rollback, userinstalled.

But I cannot see itin man page
[user@host][~]$man dnf | grep history
       · history
       The  history  command allows the user to view what has happened in past
       dnf history [list]
              The  default  history  action  is  listing all known transaction
       dnf history info [<spec>...]
       dnf history redo <transaction-spec>
       dnf history rollback <transaction-spec>
       dnf history undo <transaction-spec>
       dnf history userinstalled

Version-Release number of selected component:
dnf-0.6.4-2.fc22

Additional info:
reporter:       libreport-2.4.0
cmdline:        /usr/bin/python -OO /bin/dnf history summary 764
dso_list:       python-dnf-0.6.4-2.fc22.noarch
executable:     /bin/dnf
kernel:         4.0.0-0.rc1.git0.1.fc22.x86_64
runlevel:       N 5
type:           Python
uid:            0

Truncated backtrace:
output.py:1730:historySummaryCmd:ValueError: need more than 1 value to unpack

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 182, 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 1064, in run
    return self.command.run(self.base.extcmds)
  File "/usr/lib/python2.7/site-packages/dnf/cli/commands/__init__.py", line 1221, in run
    ret = self.output.historySummaryCmd(extcmds)
  File "/usr/lib/python2.7/site-packages/dnf/cli/output.py", line 1730, in historySummaryCmd
    tids, printall = self._history_list_transactions(extcmds)
ValueError: need more than 1 value to unpack

Local variables in innermost frame:
self: <dnf.cli.output.Output object at 0x7f19197d46d0>
extcmds: [u'summary', u'764']