pytest: Reproduce waitblockheight timeout issue #4309

tests/plugins/endlesswaitblockheight.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+"""Simple plugin to cause a waitblockheight that times out.
+
+We report an error with a future blockheight, which causes the sender
+to wait, and ultimately retry, excluding us because we misbehaved.
+
+"""
+
+
+from pyln.client import Plugin
+plugin = Plugin()
+
+
+@plugin.hook('htlc_accepted')
+def on_htlc_accepted(onion, htlc, **kwargs):
+    return {
+        'result': "fail",
+        "failure_message": "400f00000000000000007fffffff",  # Bogus error with INT32_MAX as blockheight
+    }
+
+
+plugin.run()