Cannot run agl-demo-control-panel

With current HEAD of agl-demo-control-panel (i.e. commit 9af16ad) , I get the following exception when trying to run it:

This is on my Fedora desktop where it worked on Thursday with a tree that was effectively at commit 20fe2d13 (I had cherry-picked that from Gerrit to test).  Given how much is in commit 9af16ad to attempt to unpick, it may be better if you do not update changes in Gerrit with multiple fixes and try to stick with one functional change per commit even if that's more review load for us.