testing: make sure we don't see gossip in bad order.

This is something which generally shouldn't happen, but we didn't
notice it previously.

We ignore this warning in the case where a channel was deleted: this
happens because one side can send an update while the other notices
that the channel is closed.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_lightningd.py

@@ -299,6 +299,13 @@ class BaseLightningDTests(unittest.TestCase):
             return 1
         return 0
 
+    def checkBadGossipOrder(self, node):
+        # We can have a race where we notice a channel deleted and someone
+        # sends an update.
+        if node.daemon.is_in_log('Bad gossip order') and not node.daemon.is_in_log('Deleting channel'):
+            return 1
+        return 0
+
     def tearDown(self):
         ok = self.node_factory.killall([not n.may_fail for n in self.node_factory.nodes])
         self.executor.shutdown(wait=False)
@@ -322,6 +329,11 @@ class BaseLightningDTests(unittest.TestCase):
         if err_count:
             raise ValueError("{} nodes had unexpected reconnections".format(err_count))
 
+        for node in self.node_factory.nodes:
+            err_count += self.checkBadGossipOrder(node)
+        if err_count:
+            raise ValueError("{} nodes had bad gossip order".format(err_count))
+
         if not ok:
             raise Exception("At least one lightning exited with unexpected non-zero return code")