pytest: test (failing) for not crashing if plugin fails to exec via plugin startdir

It hits the new assert(): before that (tested!) it actually kills everything and logs you out.

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

tests/plugins/badinterp.py

@@ -0,0 +1,15 @@
+#!/some/bad/path/to/python3
+from pyln.client import Plugin
+import os
+import time
+
+plugin = Plugin()
+
+
+@plugin.init()
+def init(options, configuration, plugin):
+    plugin.log("slow_init.py initializing {}".format(configuration))
+    time.sleep(int(os.getenv('SLOWINIT_TIME', "0")))
+
+
+plugin.run()

tests/test_plugin.py

@@ -4273,3 +4273,10 @@ def test_renepay_not_important(node_factory):
     # But we don't shut down, and we can restrart.
     assert [p['name'] for p in l1.rpc.listconfigs()['plugins'] if p['name'] == 'cln-renepay'] == []
     l1.rpc.plugin_start(os.path.join(os.getcwd(), 'plugins/cln-renepay'))
+
+
+@pytest.mark.xfail(strict=True)
+def test_plugin_startdir_lol(node_factory):
+    """Though we fail to start many of them, we don't crash!"""
+    l1 = node_factory.get_node(allow_broken_log=True)
+    l1.rpc.plugin_startdir(os.path.join(os.getcwd(), 'tests/plugins'))