We're trying to get lagSeconds out of
db.runCommand(

{serverStatus : 1, repl : 2}

)
or
db._adminCommand(

{serverStatus:1,repl:2}

)
or
(python)
serverStatus = db.command(bson.son.SON([('serverStatus', 1), ('repl', 2)]))

getting the following error in the master's log
assertion 10057 unauthorized db:local lock type:-1

and this message is on the slave object (notice it doesn't list the sources at all)

"repl" :

{ "ismaster" : false, "sources" : [ ] }

,
"assertion" : "nextSafe():

{ $err: \"unauthorized db:local lock type:-1 client:10.0.0.27\", code: 10057 }

",
"assertionCode" : 13106,
"errmsg" : "db assertion failure",
"ok" : 0

I'm authenticating as the repl user, which exists on both master and slave, in the local db
db.auth("repl", "...");

I'm working on a authenticated nagios monitoring plugin..