should reject an scxml document containing assign without @Location
Created by: mattoshry
Per [1], assign/@Location is required.
SCION should reject the following:
<scxml xmlns="http://www.w3.org/2005/07/scxml"
version="1.0">
<state id="uber">
<onentry>
<!-- missing location -->
<assign expr="'foo'"/>
</onentry>
<transition event="*" target="fail">
<log expr="'unhandled event ' + JSON.stringify(_event)"/>
</transition>
</state>
<final id="fail"/>
</scxml>