add debug_name to "cannot iterate X with Y REPR" message

Author: timo

src/6model/reprs/MVMIter.c

@@ -301,8 +301,8 @@ MVMObject * MVM_iter(MVMThreadContext *tc, MVMObject *target) {
             iterator = (MVMIter *)MVM_iter(tc, ctx_hash);
         }
         else {
-            MVM_exception_throw_adhoc(tc, "Cannot iterate object with %s representation",
-                REPR(target)->name);
+            MVM_exception_throw_adhoc(tc, "Cannot iterate object with %s representation (%s)",
+                REPR(target)->name, STABLE(target)->debug_name);
         }
     });
     return (MVMObject *)iterator;