Give better feedback when skill isn't loaded
Give better feedback when skill isn't loaded

If a skill required for a test case isn't loaded an exception will be
raised.

MycroftAI/mycroft-core,forslund/mycroft-core,MycroftAI/mycroft-core,linuxipho/mycroft-core,linuxipho/mycroft-core,Dark5ide/mycroft-core,forslund/mycroft-core,Dark5ide/mycroft-core