Failed test 'psql query died successfully after SIGQUIT'

Hi,

Does anyone have any thoughts on why Travis CI might be failing
occasionally as shown below, but the build farm apparently doesn't?
It's not alien technology, it's just Ubuntu Linux running on a virtual
machine. One thing that it does slightly differently is "make
-Otarget -j3 check-world" but I don't see why -j3 would break
something like that specifically, except perhaps by overloading the
system in a way that affects timing. And yet we have all many of fast
and slow machines in the BF, so I don't know.

https://travis-ci.org/postgresql-cfbot/postgresql/builds/334253917

t/012_subtransactions.pl ............. ok
# aborting wait: program timed out
# stream contents: >><<
# pattern searched for: (?^m:psql-connected)
# Failed test 'monitor connected'
# at t/013_crash_restart.pl line 95.
# aborting wait: program timed out
# stream contents: >><<
# pattern searched for: (?^m:WARNING: terminating connection because
of crash of another server process|server closed the connection
unexpectedly)
# Failed test 'psql query died successfully after SIGQUIT'
# at t/013_crash_restart.pl line 110.
# aborting wait: program timed out
# stream contents: >>psql:<stdin>:3: WARNING: terminating connection
because of crash of another server process
# DETAIL: The postmaster has commanded this server process to roll
back the current transaction and exit, because another server process
exited abnormally and possibly corrupted shared memory.
# HINT: In a moment you should be able to reconnect to the database
and repeat your command.
# psql:<stdin>:3: server closed the connection unexpectedly
# This probably means the server terminated abnormally
# before or while processing the request.
# psql:<stdin>:3: connection to server was lost
# <<
# pattern searched for: (?^m:WARNING: terminating connection because
of crash of another server process|server closed the connection
unexpectedly)
# Failed test 'psql monitor died successfully after SIGQUIT'
# at t/013_crash_restart.pl line 119.
# Looks like you failed 3 tests of 18.
t/013_crash_restart.pl ...............
Dubious, test returned 3 (wstat 768, 0x300)
Failed 3/18 subtests
Test Summary Report
-------------------
t/013_crash_restart.pl (Wstat: 768 Tests: 18 Failed: 3)
Failed tests: 3, 5-6
Non-zero exit status: 3
Files=13, Tests=134, 198 wallclock secs ( 0.10 usr 0.01 sys + 35.98
cusr 10.35 csys = 46.44 CPU)
Result: FAIL
Makefile:19: recipe for target 'check' failed

--
Thomas Munro
http://www.enterprisedb.com