Laptop won't suspend with ext monitor - which package for bug?

[Colin Law]

Testing Ubuntu vivid I find my laptop will not suspend if an external
monitor is connected. It appears to be not even trying as nothing is
written to pm-suspend.log and nothing related to suspend in syslog. It
suspends ok without external monitor.  I don't know which package to
report this against.  Any suggestions.

Is the above an appropriate question for this list?  I have previously
tried ubuntu-users for such questions, usually with little response.

Colin