Using gossip_store in tests

[gijswijs]

I am trying to lift gossip messages out of gossip_store using the pyln-testing library.

This is my initial setup

# Create two nodes
opts = [{}, {}]
alice, bob = node_factory.get_nodes(2, opts=opts)

# Open Channel
alice.openchannel(bob, capacity=10**6)

# Now wait for gossip to settle and alice to learn the topology
wait_for(lambda: len(alice.rpc.listchannels()['channels']) == 2)

I then open the gossip_store with open('{}regtest/gossip_store'.format(alice.daemon.lightning_dir), 'rb') as f: and parse it similar to what the Historian plugin does with gossipd.py

But it never yields anything it can parse. It always just returns:

Exception parsing gossip message: No parser registered for type 4104
Exception parsing gossip message: No parser registered for type 4102
Exception parsing gossip message: No parser registered for type 4102

It does work if I run the plugin registered with a node, but with the pyln-testing library I can't seem to get it to work.
My development process would be much quicker if I can test it with pyln-testing instead of stopping and starting a plugin over and over again with a running node after each change in my code.