This is the functional test counterpart of PR #28891 / commit 007d6f0e85bc329040bb405ef6016339518caa66 (unfortunately, I missed it back then and only ran the unit tests -- sorry for the noise).
master branch on OpenBSD 7.4:
$ ./test/functional/rpc_net.py
2023-12-08T17:29:05.057000Z TestFramework (INFO): PRNG seed is: 6024296850131317403
2023-12-08T17:29:05.058000Z TestFramework (INFO): Initializing test directory /tmp/bitcoin_func_test_au3zchif
2023-12-08T17:29:05.618000Z TestFramework (INFO): Test getconnectioncount
2023-12-08T17:29:05.618000Z TestFramework (INFO): Test getpeerinfo
2023-12-08T17:29:06.643000Z TestFramework (INFO): Check getpeerinfo output before a version message was sent
2023-12-08T17:29:06.709000Z TestFramework (INFO): Test getnettotals
2023-12-08T17:29:06.773000Z TestFramework (INFO): Test getnetworkinfo
2023-12-08T17:29:06.978000Z TestFramework (INFO): Test addnode and getaddednodeinfo
2023-12-08T17:29:06.980000Z TestFramework (ERROR): Assertion failed
Traceback (most recent call last):
File "/home/thestack/bitcoin/test/functional/test_framework/test_framework.py", line 131, in main
self.run_test()
File "/home/thestack/bitcoin/./test/functional/rpc_net.py", line 65, in run_test
self.test_addnode_getaddednodeinfo()
File "/home/thestack/bitcoin/./test/functional/rpc_net.py", line 224, in test_addnode_getaddednodeinfo
assert_raises_rpc_error(-23, "Node already added", self.nodes[0].addnode, node=ip_port2, command='add')
File "/home/thestack/bitcoin/test/functional/test_framework/util.py", line 131, in assert_raises_rpc_error
assert try_rpc(code, message, fun, *args, **kwds), "No exception raised"
AssertionError: No exception raised
On the PR branch, the same call succeeds.