On EeePC 1015 PED (in Live mode), cpupower.service seemed to start too
early, before /sys/devices/.../scaling_available_governors was there,
and failed as a result. There were no such problems on faster machines,
but still.
Now cpupower.service will start only when 'scaling_available_governors'
file is available. cpupower.path unit handles this. If CPU frequency
scaling is not supported the file will never appear and cpupower.service
will not start at all, which is natural.
