test: Add feature_framework_rpc_failure.py

Verifies correct behavior when failing to connect to bitcoind RPC interface during setup. Parent commit fixes issues where a raised exception raised additional knock-on exceptions.

test/functional/feature_framework_rpc_failure.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+# Copyright (c) 2024 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""
+Verify failure to connect to bitcoind's RPC interface only raises one exception.
+
+Multiple exceptions being raised muddies the waters of what actually went wrong.
+We should maintain this bar of only raising one exception as long as additional
+maintenance and complexity is low.
+"""
+
+from pathlib import Path
+
+from test_framework.util import (
+    assert_equal,
+)
+from test_framework.test_framework import BitcoinTestFramework
+
+class FeatureFrameworkRPCFailure(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def setup_network(self):
+        test_name = Path(__file__).name
+        self.log.info(f"{test_name}: Setting RPC timeout to 0 to simulate an unresponsive bitcoind")
+        self.rpc_timeout = 0
+
+        try:
+            BitcoinTestFramework.setup_network(self)
+        except AssertionError as e:
+            assert_equal(str(e), "[node 0] Unable to connect to bitcoind after 0s")
+            self.log.info(f"{test_name}: Caught AssertionError with expected RPC connection failure message")
+        else:
+            raise AssertionError("Didn't raise expected error")
+
+    def run_test(self):
+        pass
+
+if __name__ == '__main__':
+    FeatureFrameworkRPCFailure(__file__).main()

test/functional/test_runner.py

@@ -402,6 +402,7 @@
     'p2p_handshake.py --v2transport',
     'feature_dirsymlinks.py',
     'feature_help.py',
+    'feature_framework_rpc_failure.py',
     'feature_shutdown.py',
     'wallet_migration.py',
     'p2p_ibd_txrelay.py',