ut0/wait_close now detects errors

Fixes #29

scone/common/chanpro.py

@@ -158,7 +158,19 @@ class Channel:
 
     async def wait_close(self):
         try:
-            await self.recv()
+            closure = await self.recv()
+            if not isinstance(closure, dict):
+                raise ValueError("Closure should be of type dict")
+
+            if not closure.get("closure"):
+                raise ValueError("Closure should have closure: True")
+
+            reason = closure.get("reason")
+            if reason != "Utensil complete":
+                raise ValueError(
+                    f"Closure was not for the right reason: expected 'Utensil complete'"
+                    f", found {reason}"
+                )
             raise RuntimeError("Message arrived when expecting closure.")
         except EOFError:
             # expected