Strange messages in log

Hi,

does somebody know reason of these messages? It appears regulary in system log, but i have no idea, what to check.

2016-12-19T16:35:25+01:00 warning []: Unable to use //tmp//yin2yang.xsl (No such file or directory).
2016-12-19T16:35:25+01:00 warning []: YANG format data models will not be available via get-schema.
2016-12-19T16:35:25+01:00 warning []: Unable to get tty (Not a tty) to get the client’s hostname (session 15021).
2016-12-19T16:35:25+01:00 warning []: Bad config ‘show_clients.sh’: uci: Entry not found

See A) in The updater is very buggy - #6 by vorner - Turris Omnia - Turris forum for these.