BIND 10 #2848: b10-cmdctl-usermgr can't execute

[BIND 10 Development]

#2848: b10-cmdctl-usermgr can't execute
-------------------------------------+-------------------------------------
            Reporter:  champion_xie  |                        Owner:
                Type:  defect        |                       Status:  new
            Priority:  very high     |                    Milestone:  New
           Component:  cmd-ctl       |  Tasks
            Keywords:                |                   Resolution:
           Sensitive:  0             |                 CVSS Scoring:
         Sub-Project:  DNS           |              Defect Severity:  Very
Estimated Difficulty:  0             |  High
         Total Hours:  0             |  Feature Depending on Ticket:
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Comment (by jelte):

 Since ticket #2713, b10-cmdctl-usermgr needs an explicit command (add or
 delete); e.g.

 {{{
 b10-cmdctl-usermgr add
 }}}

 to add a user.

 But the error it currently gives is obviously not clear :)

 So I think we should print the usage() if the error BAD_ARGUMENTS arises,
 that the output in the above case would be:
 {{{
 #./b10-cmdctl-usermgr
 Error: no command specified
 Usage: b10-cmdctl-usermgr [options] <command> [username] [password]

 Arguments:
   command               either 'add' or 'delete'
   username              the username to add or delete
   password              the password to set for the added user

 If username or password are not specified, b10-cmdctl-usermgr will
 prompt for them. It is recommended practice to let the
 tool prompt for the password, as command-line
 arguments can be visible through history or process
 viewers.
 }}}

 It's a pretty simple change, and I've taken the liberty to provide a
 branch with the 4-line diff

-- 
Ticket URL: <http://bind10.isc.org/ticket/2848#comment:1>
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