Traceback (most recent call last):
  File "/usr/bin/hwdb-gui", line 153, in <lambda>
    self.advance.connect("clicked", lambda w: self.adv(self.xmlfile))
  File "/usr/bin/hwdb-gui", line 597, in adv
    set[2] = set[2]+self.get_xorgdata()
  File "/usr/bin/hwdb-gui", line 256, in get_xorgdata
    return retval
UnboundLocalError: local variable 'retval' referenced before assignment