Looks like a spurious Travis failure in p2p-segwit.py here: https://travis-ci.org/bitcoin/bitcoin/jobs/254520908#L5356

2017-07-17 19:06:34.660901 Unable to bind to 0.0.0.0:11211 on this computer. Bitcoin Core is probably already running.

test_runner.py and test_framework.py are very careful to not re-use ports for p2p and rpc interfaces on different nodes/tests, so perhaps another process was bound to 11211. Googling for port 11211 shows that it's memcached's default port.

Should be easy to test whether port 11211 causes problems by pushing a branch with port_seed() changed.