pytest: fail if we see 'bad reestablish' in the logs.

Really, we should use log-level more cleverly here.

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

tests/fixtures.py

@@ -124,6 +124,11 @@ def node_factory(directory, test_name, bitcoind, executor):
     if err_count:
         raise ValueError("{} nodes had bad gossip order".format(err_count))
 
+    for node in nf.nodes:
+        err_count += checkBadReestablish(node)
+    if err_count:
+        raise ValueError("{} nodes had bad reestablish".format(err_count))
+
     if not ok:
         raise Exception("At least one lightning exited with unexpected non-zero return code")
 
@@ -184,6 +189,12 @@ def checkBadGossipOrder(node):
     return 0
 
 
+def checkBadReestablish(node):
+    if node.daemon.is_in_log('Bad reestablish'):
+        return 1
+    return 0
+
+
 @pytest.fixture
 def executor():
     ex = futures.ThreadPoolExecutor(max_workers=20)