In an out_of_context (OOC) design targeting on UltraScale device, the following DRC is reported for the clock signal:
Is this DRC correct?
DRC should not report OOC clocks as unrouted or partially routed in UltraScale.
In Vivado 2015.1, this DRC will be removed for these circumstances.
You can work around this issue in Vivado versions prior to 2015.1 by reducing the severity of the RTSTAT-2 check:
set_property severity warning [get_drc_checks RTSTAT-2]