Comment 1 for bug 1433997

These are two different issues the first one has something to do with the Backlight folder of sysfs (/sys/class/backlight/...) the error you get is very similar to the error if there is no controlable backlight device but in this case their is also a NoBacklightDeviceFoundException. So here is my question have you try to run yawls on an desktop or notebook because yawls needs a hardware backlight to change the brightness value in this this file

/sys/class/backlight/[backlight device]/backlight

The second one has maybe something to do with the glade files of yawls and the newer version of glib in ubuntu 15.04.