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/fixtures.py

@@ -91,6 +91,10 @@ def node_factory(directory, test_name, bitcoind, executor):
         err_count += checkReconnect(node)
     if err_count:
         raise ValueError("{} nodes had unexpected reconnections".format(err_count))
+    for node in nf.nodes:
+        err_count += 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")
@@ -147,6 +151,12 @@ def checkReconnect(node):
     return 0
 
 
+def checkBadGossipOrder(node):
+    if node.daemon.is_in_log('Bad gossip order') and not node.daemon.is_in_log('Deleting channel'):
+        return 1
+    return 0
+
+
 @pytest.fixture
 def executor():
     ex = futures.ThreadPoolExecutor(max_workers=20)