Invert the KJob::Exec check logic
Review Request #122151 - Created Jan. 19, 2015 and discarded
docs state the failure of exec shall be checked first.
resolves the bug for me (i have the brightness control in the battery applet now)
Could this be related to /r/122029? When KAuth failed to invoke the helper tool (because of the broken service file), the ExecJob got simply stuck. This was only fixed be rebuilding PowerDevil against the fixed KAuth...