There are occasional failures of example_test on travis, which are annoying but not critical.
It will timeout while waiting for an verack on the added p2p connection:
self.nodes[2].p2p.wait_for_verack()
The issue might be that we add a p2p connection in L134 and then start the network thread: https://github.com/bitcoin/bitcoin/blob/a89221873a3ee2451c73b41bbe2d99d36f439d31/test/functional/example_test.py#L134-L139
Afterward, we don't restart the network thread, but add yet another p2p connection: https://github.com/bitcoin/bitcoin/blob/a89221873a3ee2451c73b41bbe2d99d36f439d31/test/functional/example_test.py#L190-L192
I have slight doubt that this is expected to work.