The feature_block test causes the travis machine to OOM, when run with the thread sanitizer.
The stderr says:
==27237==ERROR: ThreadSanitizer failed to allocate 0xf6000 (1007616) bytes of LargeMmapAllocator (error code: 12)
...
FATAL: ThreadSanitizer CHECK failed: /build/llvm-toolchain-3.8-_PD09B/llvm-toolchain-3.8-3.8/projects/compiler-rt/lib/sanitizer_common/sanitizer_common.cc:183 "((0 && "unable to mmap")) != (0)" (0x0, 0x0)
ERROR: Failed to mmap
(from https://travis-ci.org/bitcoin/bitcoin/jobs/588194563#L10505)
Fix this by disabling feature_block on travis. Longer term, I'd like to move away from travis, but I'll leave this for a follow-up.